diff --git a/src/browser/cssom/css_parser.zig b/src/browser/cssom/css_parser.zig
new file mode 100644
index 00000000..24879de7
--- /dev/null
+++ b/src/browser/cssom/css_parser.zig
@@ -0,0 +1,308 @@
+const std = @import("std");
+
+const CSSConstants = struct {
+    const IMPORTANT_KEYWORD = "!important";
+    const IMPORTANT_LENGTH = IMPORTANT_KEYWORD.len;
+    const URL_PREFIX = "url(";
+    const URL_PREFIX_LENGTH = URL_PREFIX.len;
+};
+
+pub const CSSParserState = enum {
+    seekName,
+    inName,
+    seekColon,
+    seekValue,
+    inValue,
+    inQuotedValue,
+    inSingleQuotedValue,
+    inUrl,
+    inImportant,
+};
+
+pub const CSSDeclaration = struct {
+    name: []const u8,
+    value: []const u8,
+    is_important: bool,
+
+    pub fn init(name: []const u8, value: []const u8, is_important: bool) CSSDeclaration {
+        return .{
+            .name = name,
+            .value = value,
+            .is_important = is_important,
+        };
+    }
+};
+
+pub const CSSParser = struct {
+    state: CSSParserState,
+    name_start: usize,
+    name_end: usize,
+    value_start: usize,
+    position: usize,
+    paren_depth: usize,
+    escape_next: bool,
+
+    pub fn init() CSSParser {
+        return .{
+            .state = .seekName,
+            .name_start = 0,
+            .name_end = 0,
+            .value_start = 0,
+            .position = 0,
+            .paren_depth = 0,
+            .escape_next = false,
+        };
+    }
+
+    pub fn parseDeclarations(text: []const u8, allocator: std.mem.Allocator) ![]CSSDeclaration {
+        var parser = init();
+        var declarations = std.ArrayList(CSSDeclaration).init(allocator);
+        errdefer declarations.deinit();
+
+        while (parser.position < text.len) {
+            const c = text[parser.position];
+
+            switch (parser.state) {
+                .seekName => {
+                    if (!std.ascii.isWhitespace(c)) {
+                        parser.name_start = parser.position;
+                        parser.state = .inName;
+                        continue;
+                    }
+                },
+                .inName => {
+                    if (c == ':') {
+                        parser.name_end = parser.position;
+                        parser.state = .seekValue;
+                    } else if (std.ascii.isWhitespace(c)) {
+                        parser.name_end = parser.position;
+                        parser.state = .seekColon;
+                    }
+                },
+                .seekColon => {
+                    if (c == ':') {
+                        parser.state = .seekValue;
+                    } else if (!std.ascii.isWhitespace(c)) {
+                        parser.state = .seekName;
+                        continue;
+                    }
+                },
+                .seekValue => {
+                    if (!std.ascii.isWhitespace(c)) {
+                        parser.value_start = parser.position;
+                        if (c == '"') {
+                            parser.state = .inQuotedValue;
+                        } else if (c == '\'') {
+                            parser.state = .inSingleQuotedValue;
+                        } else if (c == 'u' and parser.position + 3 < text.len and
+                            std.mem.eql(u8, text[parser.position .. parser.position + 4], CSSConstants.URL_PREFIX))
+                        {
+                            parser.state = .inUrl;
+                            parser.paren_depth = 1;
+                            parser.position += 3;
+                        } else {
+                            parser.state = .inValue;
+                            continue;
+                        }
+                    }
+                },
+                .inValue => {
+                    if (parser.escape_next) {
+                        parser.escape_next = false;
+                    } else if (c == '\\') {
+                        parser.escape_next = true;
+                    } else if (c == '(') {
+                        parser.paren_depth += 1;
+                    } else if (c == ')' and parser.paren_depth > 0) {
+                        parser.paren_depth -= 1;
+                    } else if (c == ';' and parser.paren_depth == 0) {
+                        try parser.finishDeclaration(text, &declarations);
+                        parser.state = .seekName;
+                    }
+                },
+                .inQuotedValue => {
+                    if (parser.escape_next) {
+                        parser.escape_next = false;
+                    } else if (c == '\\') {
+                        parser.escape_next = true;
+                    } else if (c == '"') {
+                        parser.state = .inValue;
+                    }
+                },
+                .inSingleQuotedValue => {
+                    if (parser.escape_next) {
+                        parser.escape_next = false;
+                    } else if (c == '\\') {
+                        parser.escape_next = true;
+                    } else if (c == '\'') {
+                        parser.state = .inValue;
+                    }
+                },
+                .inUrl => {
+                    if (parser.escape_next) {
+                        parser.escape_next = false;
+                    } else if (c == '\\') {
+                        parser.escape_next = true;
+                    } else if (c == '(') {
+                        parser.paren_depth += 1;
+                    } else if (c == ')') {
+                        parser.paren_depth -= 1;
+                        if (parser.paren_depth == 0) {
+                            parser.state = .inValue;
+                        }
+                    }
+                },
+                .inImportant => {},
+            }
+
+            parser.position += 1;
+        }
+
+        try parser.finalize(text, &declarations);
+
+        return declarations.toOwnedSlice();
+    }
+
+    fn finishDeclaration(self: *CSSParser, text: []const u8, declarations: *std.ArrayList(CSSDeclaration)) !void {
+        const name = std.mem.trim(u8, text[self.name_start..self.name_end], &std.ascii.whitespace);
+        if (name.len == 0) return;
+
+        const raw_value = text[self.value_start..self.position];
+        const value = std.mem.trim(u8, raw_value, &std.ascii.whitespace);
+
+        var final_value = value;
+        var is_important = false;
+
+        if (std.mem.endsWith(u8, value, CSSConstants.IMPORTANT_KEYWORD)) {
+            is_important = true;
+            final_value = std.mem.trim(u8, value[0 .. value.len - CSSConstants.IMPORTANT_LENGTH], &std.ascii.whitespace);
+        }
+
+        const declaration = CSSDeclaration.init(name, final_value, is_important);
+        try declarations.append(declaration);
+    }
+
+    fn finalize(self: *CSSParser, text: []const u8, declarations: *std.ArrayList(CSSDeclaration)) !void {
+        if (self.state == .inValue) {
+            const name = text[self.name_start..self.name_end];
+            const trimmed_name = std.mem.trim(u8, name, &std.ascii.whitespace);
+
+            if (trimmed_name.len > 0) {
+                const raw_value = text[self.value_start..self.position];
+                const value = std.mem.trim(u8, raw_value, &std.ascii.whitespace);
+
+                var final_value = value;
+                var is_important = false;
+                if (std.mem.endsWith(u8, value, CSSConstants.IMPORTANT_KEYWORD)) {
+                    is_important = true;
+                    final_value = std.mem.trim(u8, value[0 .. value.len - CSSConstants.IMPORTANT_LENGTH], &std.ascii.whitespace);
+                }
+
+                const declaration = CSSDeclaration.init(trimmed_name, final_value, is_important);
+                try declarations.append(declaration);
+            }
+        }
+    }
+
+    pub fn getState(self: *const CSSParser) CSSParserState {
+        return self.state;
+    }
+
+    pub fn getPosition(self: *const CSSParser) usize {
+        return self.position;
+    }
+
+    pub fn reset(self: *CSSParser) void {
+        self.* = init();
+    }
+};
+
+const testing = std.testing;
+
+test "CSSParser - Simple property" {
+    const text = "color: red;";
+    const allocator = testing.allocator;
+
+    const declarations = try CSSParser.parseDeclarations(text, allocator);
+    defer allocator.free(declarations);
+
+    try testing.expect(declarations.len == 1);
+    try testing.expectEqualStrings("color", declarations[0].name);
+    try testing.expectEqualStrings("red", declarations[0].value);
+    try testing.expect(!declarations[0].is_important);
+}
+
+test "CSSParser - Property with !important" {
+    const text = "margin: 10px !important;";
+    const allocator = testing.allocator;
+
+    const declarations = try CSSParser.parseDeclarations(text, allocator);
+    defer allocator.free(declarations);
+
+    try testing.expect(declarations.len == 1);
+    try testing.expectEqualStrings("margin", declarations[0].name);
+    try testing.expectEqualStrings("10px", declarations[0].value);
+    try testing.expect(declarations[0].is_important);
+}
+
+test "CSSParser - Multiple properties" {
+    const text = "color: red; font-size: 12px; margin: 5px !important;";
+    const allocator = testing.allocator;
+
+    const declarations = try CSSParser.parseDeclarations(text, allocator);
+    defer allocator.free(declarations);
+
+    try testing.expect(declarations.len == 3);
+
+    try testing.expectEqualStrings("color", declarations[0].name);
+    try testing.expectEqualStrings("red", declarations[0].value);
+    try testing.expect(!declarations[0].is_important);
+
+    try testing.expectEqualStrings("font-size", declarations[1].name);
+    try testing.expectEqualStrings("12px", declarations[1].value);
+    try testing.expect(!declarations[1].is_important);
+
+    try testing.expectEqualStrings("margin", declarations[2].name);
+    try testing.expectEqualStrings("5px", declarations[2].value);
+    try testing.expect(declarations[2].is_important);
+}
+
+test "CSSParser - Quoted value with semicolon" {
+    const text = "content: \"Hello; world!\";";
+    const allocator = testing.allocator;
+
+    const declarations = try CSSParser.parseDeclarations(text, allocator);
+    defer allocator.free(declarations);
+
+    try testing.expect(declarations.len == 1);
+    try testing.expectEqualStrings("content", declarations[0].name);
+    try testing.expectEqualStrings("\"Hello; world!\"", declarations[0].value);
+    try testing.expect(!declarations[0].is_important);
+}
+
+test "CSSParser - URL value" {
+    const text = "background-image: url(\"test.png\");";
+    const allocator = testing.allocator;
+
+    const declarations = try CSSParser.parseDeclarations(text, allocator);
+    defer allocator.free(declarations);
+
+    try testing.expect(declarations.len == 1);
+    try testing.expectEqualStrings("background-image", declarations[0].name);
+    try testing.expectEqualStrings("url(\"test.png\")", declarations[0].value);
+    try testing.expect(!declarations[0].is_important);
+}
+
+test "CSSParser - Whitespace handling" {
+    const text = "  color  :  purple  ;  margin  :  10px  ;  ";
+    const allocator = testing.allocator;
+
+    const declarations = try CSSParser.parseDeclarations(text, allocator);
+    defer allocator.free(declarations);
+
+    try testing.expect(declarations.len == 2);
+    try testing.expectEqualStrings("color", declarations[0].name);
+    try testing.expectEqualStrings("purple", declarations[0].value);
+    try testing.expectEqualStrings("margin", declarations[1].name);
+    try testing.expectEqualStrings("10px", declarations[1].value);
+}
diff --git a/src/browser/cssom/css_style_declaration.zig b/src/browser/cssom/css_style_declaration.zig
new file mode 100644
index 00000000..359d9dc9
--- /dev/null
+++ b/src/browser/cssom/css_style_declaration.zig
@@ -0,0 +1,236 @@
+// Copyright (C) 2023-2024  Lightpanda (Selecy SAS)
+//
+// Francis Bouvier <francis@lightpanda.io>
+// Pierre Tachoire <pierre@lightpanda.io>
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as
+// published by the Free Software Foundation, either version 3 of the
+// License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+const std = @import("std");
+
+const CSSParser = @import("./css_parser.zig").CSSParser;
+const CSSValueAnalyzer = @import("./css_value_analyzer.zig").CSSValueAnalyzer;
+const SessionState = @import("../env.zig").SessionState;
+
+pub const Interfaces = .{
+    CSSStyleDeclaration,
+    CSSRule,
+};
+
+const CSSRule = struct {};
+
+pub const CSSStyleDeclaration = struct {
+    store: std.StringHashMapUnmanaged(Property),
+    order: std.ArrayListUnmanaged([]const u8),
+
+    const Property = struct {
+        value: []const u8,
+        priority: bool,
+    };
+
+    pub fn get_cssFloat(self: *const CSSStyleDeclaration) []const u8 {
+        return self._getPropertyValue("float");
+    }
+
+    pub fn set_cssFloat(self: *CSSStyleDeclaration, value: ?[]const u8, state: *SessionState) !void {
+        const final_value = value orelse "";
+        return self._setProperty("float", final_value, null, state);
+    }
+
+    pub fn get_cssText(self: *const CSSStyleDeclaration, state: *SessionState) ![]const u8 {
+        var buffer = std.ArrayList(u8).init(state.arena);
+        const writer = buffer.writer();
+        for (self.order.items) |name| {
+            const prop = self.store.get(name).?;
+            const escaped = try CSSValueAnalyzer.escapeCSSValue(state.arena, prop.value);
+            try writer.print("{s}: {s}", .{ name, escaped });
+            if (prop.priority) try writer.writeAll(" !important");
+            try writer.writeAll("; ");
+        }
+        return buffer.toOwnedSlice();
+    }
+
+    // TODO Propagate also upward to parent node
+    pub fn set_cssText(self: *CSSStyleDeclaration, text: []const u8, state: *SessionState) !void {
+        var store_it = self.store.iterator();
+        while (store_it.next()) |entry| {
+            state.arena.free(entry.key_ptr.*);
+            state.arena.free(entry.value_ptr.value);
+        }
+        self.store.clearRetainingCapacity();
+        for (self.order.items) |name| state.arena.free(name);
+        self.order.clearRetainingCapacity();
+
+        const declarations = try CSSParser.parseDeclarations(text, state.arena);
+        defer state.arena.free(declarations);
+
+        for (declarations) |decl| {
+            if (!CSSValueAnalyzer.isValidPropertyName(decl.name)) continue;
+            const priority: ?[]const u8 = if (decl.is_important) "important" else null;
+            try self._setProperty(decl.name, decl.value, priority, state);
+        }
+    }
+
+    pub fn get_length(self: *const CSSStyleDeclaration) usize {
+        return self.order.items.len;
+    }
+
+    pub fn get_parentRule() ?CSSRule {
+        return null;
+    }
+
+    pub fn _getPropertyPriority(self: *const CSSStyleDeclaration, name: []const u8) []const u8 {
+        return if (self.store.get(name)) |prop| (if (prop.priority) "important" else "") else "";
+    }
+
+    // TODO should handle properly shorthand properties and canonical forms
+    pub fn _getPropertyValue(self: *const CSSStyleDeclaration, name: []const u8) []const u8 {
+        return if (self.store.get(name)) |prop| prop.value else "";
+    }
+
+    pub fn _item(self: *const CSSStyleDeclaration, index: usize) []const u8 {
+        return if (index < self.order.items.len) self.order.items[index] else "";
+    }
+
+    pub fn _removeProperty(self: *CSSStyleDeclaration, name: []const u8, state: *SessionState) ![]const u8 {
+        if (self.store.get(name)) |prop| {
+            const value_copy = try state.arena.dupe(u8, prop.value);
+            _ = self.store.remove(name);
+            state.arena.free(prop.value);
+            var i: usize = 0;
+            while (i < self.order.items.len) : (i += 1) {
+                if (std.mem.eql(u8, self.order.items[i], name)) {
+                    state.arena.free(self.order.items[i]);
+                    _ = self.order.orderedRemove(i);
+                    break;
+                }
+            }
+            return value_copy;
+        }
+        return "";
+    }
+
+    pub fn _setProperty(self: *CSSStyleDeclaration, name: []const u8, value: []const u8, priority: ?[]const u8, state: *SessionState) !void {
+        const is_important = priority != null and std.ascii.eqlIgnoreCase(priority.?, "important");
+
+        const value_copy = try state.arena.dupe(u8, value);
+
+        if (!self.store.contains(name)) {
+            const name_copy = try state.arena.dupe(u8, name);
+            try self.order.append(state.arena, name_copy);
+            try self.store.put(state.arena, name_copy, Property{ .value = value_copy, .priority = is_important });
+        } else {
+            const prev = self.store.get(name).?;
+            state.arena.free(prev.value);
+            try self.store.put(state.arena, name, Property{ .value = value_copy, .priority = is_important });
+        }
+    }
+};
+
+const testing = @import("../../testing.zig");
+
+test "CSSOM.CSSStyleDeclaration" {
+    var runner = try testing.jsRunner(testing.tracking_allocator, .{});
+    defer runner.deinit();
+
+    try runner.testCases(&.{
+        .{ "let style = document.getElementById('content').style", "undefined" },
+        .{ "style.cssText = 'color: red; font-size: 12px; margin: 5px !important;'", "color: red; font-size: 12px; margin: 5px !important;" },
+        .{ "style.length", "3" },
+    }, .{});
+
+    try runner.testCases(&.{
+        .{ "style.getPropertyValue('color')", "red" },
+        .{ "style.getPropertyValue('font-size')", "12px" },
+        .{ "style.getPropertyValue('unknown-property')", "" },
+
+        .{ "style.getPropertyPriority('margin')", "important" },
+        .{ "style.getPropertyPriority('color')", "" },
+        .{ "style.getPropertyPriority('unknown-property')", "" },
+
+        .{ "style.item(0)", "color" },
+        .{ "style.item(1)", "font-size" },
+        .{ "style.item(2)", "margin" },
+        .{ "style.item(3)", "" },
+    }, .{});
+
+    try runner.testCases(&.{
+        .{ "style.setProperty('background-color', 'blue')", "undefined" },
+        .{ "style.getPropertyValue('background-color')", "blue" },
+        .{ "style.length", "4" },
+
+        .{ "style.setProperty('color', 'green')", "undefined" },
+        .{ "style.getPropertyValue('color')", "green" },
+        .{ "style.length", "4" },
+
+        .{ "style.setProperty('padding', '10px', 'important')", "undefined" },
+        .{ "style.getPropertyValue('padding')", "10px" },
+        .{ "style.getPropertyPriority('padding')", "important" },
+
+        .{ "style.setProperty('border', '1px solid black', 'IMPORTANT')", "undefined" },
+        .{ "style.getPropertyPriority('border')", "important" },
+    }, .{});
+
+    try runner.testCases(&.{
+        .{ "style.removeProperty('color')", "green" },
+        .{ "style.getPropertyValue('color')", "" },
+        .{ "style.length", "5" },
+
+        .{ "style.removeProperty('unknown-property')", "" },
+    }, .{});
+
+    try runner.testCases(&.{
+        .{ "style.cssText.includes('font-size: 12px;')", "true" },
+        .{ "style.cssText.includes('margin: 5px !important;')", "true" },
+        .{ "style.cssText.includes('padding: 10px !important;')", "true" },
+        .{ "style.cssText.includes('border: 1px solid black !important;')", "true" },
+
+        .{ "style.cssText = 'color: purple; text-align: center;'", "color: purple; text-align: center;" },
+        .{ "style.length", "2" },
+        .{ "style.getPropertyValue('color')", "purple" },
+        .{ "style.getPropertyValue('text-align')", "center" },
+        .{ "style.getPropertyValue('font-size')", "" },
+
+        .{ "style.setProperty('cont', 'Hello; world!')", "undefined" },
+        .{ "style.getPropertyValue('cont')", "Hello; world!" },
+
+        .{ "style.cssText = 'content: \"Hello; world!\"; background-image: url(\"test.png\");'", "content: \"Hello; world!\"; background-image: url(\"test.png\");" },
+        .{ "style.getPropertyValue('content')", "\"Hello; world!\"" },
+        .{ "style.getPropertyValue('background-image')", "url(\"test.png\")" },
+    }, .{});
+
+    try runner.testCases(&.{
+        .{ "style.cssFloat", "" },
+        .{ "style.cssFloat = 'left'", "left" },
+        .{ "style.cssFloat", "left" },
+        .{ "style.getPropertyValue('float')", "left" },
+
+        .{ "style.cssFloat = 'right'", "right" },
+        .{ "style.cssFloat", "right" },
+
+        .{ "style.cssFloat = null", "null" },
+        .{ "style.cssFloat", "" },
+    }, .{});
+
+    try runner.testCases(&.{
+        .{ "style.setProperty('display', '')", "undefined" },
+        .{ "style.getPropertyValue('display')", "" },
+
+        .{ "style.cssText = '  color  :  purple  ;  margin  :  10px  ;  '", "  color  :  purple  ;  margin  :  10px  ;  " },
+        .{ "style.getPropertyValue('color')", "purple" },
+        .{ "style.getPropertyValue('margin')", "10px" },
+
+        .{ "style.setProperty('border-bottom-left-radius', '5px')", "undefined" },
+        .{ "style.getPropertyValue('border-bottom-left-radius')", "5px" },
+    }, .{});
+}
diff --git a/src/browser/cssom/css_value_analyzer.zig b/src/browser/cssom/css_value_analyzer.zig
new file mode 100644
index 00000000..9b098aa8
--- /dev/null
+++ b/src/browser/cssom/css_value_analyzer.zig
@@ -0,0 +1,327 @@
+// Copyright (C) 2023-2024  Lightpanda (Selecy SAS)
+//
+// Francis Bouvier <francis@lightpanda.io>
+// Pierre Tachoire <pierre@lightpanda.io>
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as
+// published by the Free Software Foundation, either version 3 of the
+// License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+const std = @import("std");
+
+pub const CSSValueAnalyzer = struct {
+    pub fn isNumericWithUnit(value: []const u8) bool {
+        if (value.len == 0) return false;
+
+        if (!std.ascii.isDigit(value[0]) and
+            value[0] != '+' and value[0] != '-' and value[0] != '.')
+        {
+            return false;
+        }
+
+        var i: usize = 0;
+        var has_digit = false;
+        var decimal_point = false;
+
+        while (i < value.len) : (i += 1) {
+            const c = value[i];
+            if (std.ascii.isDigit(c)) {
+                has_digit = true;
+            } else if (c == '.' and !decimal_point) {
+                decimal_point = true;
+            } else if ((c == 'e' or c == 'E') and has_digit) {
+                i += 1;
+                if (i < value.len and (value[i] == '+' or value[i] == '-')) {
+                    i += 1;
+                }
+                var has_exp_digits = false;
+                while (i < value.len and std.ascii.isDigit(value[i])) : (i += 1) {
+                    has_exp_digits = true;
+                }
+                if (!has_exp_digits) return false;
+                break;
+            } else if (c != '-' and c != '+') {
+                break;
+            }
+        }
+
+        if (!has_digit) return false;
+
+        if (i == value.len) return true;
+
+        const unit = value[i..];
+        return CSSKeywords.isValidUnit(unit);
+    }
+
+    pub fn isHexColor(value: []const u8) bool {
+        if (!std.mem.startsWith(u8, value, "#")) return false;
+
+        const hex_part = value[1..];
+        if (hex_part.len != 3 and hex_part.len != 6 and hex_part.len != 8) return false;
+
+        for (hex_part) |c| {
+            if (!std.ascii.isHex(c)) return false;
+        }
+
+        return true;
+    }
+
+    pub fn isMultiValueProperty(value: []const u8) bool {
+        var parts = std.mem.splitAny(u8, value, " ");
+        var multi_value_parts: usize = 0;
+        var all_parts_valid = true;
+
+        while (parts.next()) |part| {
+            if (part.len == 0) continue;
+            multi_value_parts += 1;
+
+            const is_numeric = isNumericWithUnit(part);
+            const is_hex_color = isHexColor(part);
+            const is_known_keyword = CSSKeywords.isKnownKeyword(part);
+            const is_function = CSSKeywords.startsWithFunction(part);
+
+            if (!is_numeric and !is_hex_color and !is_known_keyword and !is_function) {
+                all_parts_valid = false;
+                break;
+            }
+        }
+
+        return multi_value_parts >= 2 and all_parts_valid;
+    }
+
+    pub fn isAlreadyQuoted(value: []const u8) bool {
+        return value.len >= 2 and ((value[0] == '"' and value[value.len - 1] == '"') or
+            (value[0] == '\'' and value[value.len - 1] == '\''));
+    }
+
+    pub fn isValidPropertyName(name: []const u8) bool {
+        if (name.len == 0) return false;
+
+        const first_char = name[0];
+        if (!std.ascii.isAlphabetic(first_char) and first_char != '-') {
+            return false;
+        }
+
+        for (name[1..]) |c| {
+            if (!std.ascii.isAlphanumeric(c) and c != '-') {
+                return false;
+            }
+        }
+
+        return true;
+    }
+
+    pub fn extractImportant(value: []const u8) struct { value: []const u8, is_important: bool } {
+        const trimmed = std.mem.trim(u8, value, &std.ascii.whitespace);
+
+        if (std.mem.endsWith(u8, trimmed, "!important")) {
+            const clean_value = std.mem.trim(u8, trimmed[0 .. trimmed.len - 10], &std.ascii.whitespace);
+            return .{ .value = clean_value, .is_important = true };
+        }
+
+        return .{ .value = trimmed, .is_important = false };
+    }
+
+    pub fn needsQuotes(value: []const u8) bool {
+        if (value.len == 0) return true;
+        if (isAlreadyQuoted(value)) return false;
+
+        const has_spaces = std.mem.indexOf(u8, value, " ") != null;
+        const has_special_chars = CSSKeywords.containsSpecialChar(value);
+        const is_url = std.mem.startsWith(u8, value, "url(");
+        const is_function = CSSKeywords.startsWithFunction(value);
+
+        const space_requires_quotes = has_spaces and
+            !isMultiValueProperty(value) and
+            !is_url and
+            !is_function;
+
+        return has_special_chars or space_requires_quotes;
+    }
+
+    pub fn escapeCSSValue(allocator: std.mem.Allocator, value: []const u8) ![]const u8 {
+        var out = std.ArrayList(u8).init(allocator);
+        errdefer out.deinit();
+        const writer = out.writer();
+
+        if (isAlreadyQuoted(value)) {
+            try writer.writeAll(value);
+            return out.toOwnedSlice();
+        }
+
+        const needs_quotes = needsQuotes(value);
+
+        if (needs_quotes) {
+            try writer.writeByte('"');
+
+            for (value) |c| {
+                switch (c) {
+                    '"' => try writer.writeAll("\\\""),
+                    '\\' => try writer.writeAll("\\\\"),
+                    '\n' => try writer.writeAll("\\A "),
+                    '\r' => try writer.writeAll("\\D "),
+                    '\t' => try writer.writeAll("\\9 "),
+                    0...8, 11, 12, 14...31, 127 => {
+                        try writer.print("\\{x}", .{c});
+                        if (c + 1 < value.len and std.ascii.isHex(value[c + 1])) {
+                            try writer.writeByte(' ');
+                        }
+                    },
+                    else => try writer.writeByte(c),
+                }
+            }
+
+            try writer.writeByte('"');
+        } else {
+            try writer.writeAll(value);
+        }
+
+        return out.toOwnedSlice();
+    }
+
+    pub fn isKnownKeyword(value: []const u8) bool {
+        return CSSKeywords.isKnownKeyword(value);
+    }
+
+    pub fn containsSpecialChar(value: []const u8) bool {
+        return CSSKeywords.containsSpecialChar(value);
+    }
+};
+
+const CSSKeywords = struct {
+    const BorderStyles = [_][]const u8{
+        "none", "solid", "dotted", "dashed", "double", "groove", "ridge", "inset", "outset",
+    };
+
+    const ColorNames = [_][]const u8{
+        "black",        "white",   "red", "green", "blue", "yellow", "purple", "gray", "transparent",
+        "currentColor", "inherit",
+    };
+
+    const PositionKeywords = [_][]const u8{
+        "auto", "center", "left", "right", "top", "bottom",
+    };
+
+    const BackgroundRepeat = [_][]const u8{
+        "repeat", "no-repeat", "repeat-x", "repeat-y", "space", "round",
+    };
+
+    const FontStyles = [_][]const u8{
+        "normal", "italic", "oblique", "bold", "bolder", "lighter",
+    };
+
+    const FontSizes = [_][]const u8{
+        "xx-small", "x-small", "small", "medium", "large", "x-large", "xx-large",
+        "smaller",  "larger",
+    };
+
+    const FontFamilies = [_][]const u8{
+        "serif", "sans-serif", "monospace", "cursive", "fantasy", "system-ui",
+    };
+
+    const CSSGlobal = [_][]const u8{
+        "initial", "inherit", "unset", "revert",
+    };
+
+    const DisplayValues = [_][]const u8{
+        "block", "inline", "inline-block", "flex", "grid", "none",
+    };
+
+    const LengthUnits = [_][]const u8{
+        "px", "em", "rem", "vw", "vh", "vmin", "vmax", "%", "pt", "pc", "in", "cm", "mm",
+        "ex", "ch", "fr",
+    };
+
+    const AngleUnits = [_][]const u8{
+        "deg", "rad", "grad", "turn",
+    };
+
+    const TimeUnits = [_][]const u8{
+        "s", "ms",
+    };
+
+    const FrequencyUnits = [_][]const u8{
+        "Hz", "kHz",
+    };
+
+    const ResolutionUnits = [_][]const u8{
+        "dpi", "dpcm", "dppx",
+    };
+
+    const SpecialChars = [_]u8{
+        '"', '\'', ';', '{', '}', '\\', '<', '>', '/',
+    };
+
+    const Functions = [_][]const u8{
+        "rgb",             "rgba",            "hsl",            "hsla",      "url",    "calc",  "var",  "attr",
+        "linear-gradient", "radial-gradient", "conic-gradient", "translate", "rotate", "scale", "skew", "matrix",
+    };
+
+    pub fn isKnownKeyword(value: []const u8) bool {
+        const all_categories = [_][]const []const u8{
+            &BorderStyles,  &ColorNames, &PositionKeywords, &BackgroundRepeat,
+            &FontStyles,    &FontSizes,  &FontFamilies,     &CSSGlobal,
+            &DisplayValues,
+        };
+
+        for (all_categories) |category| {
+            for (category) |keyword| {
+                if (std.mem.eql(u8, value, keyword)) {
+                    return true;
+                }
+            }
+        }
+
+        return false;
+    }
+
+    pub fn containsSpecialChar(value: []const u8) bool {
+        for (value) |c| {
+            for (SpecialChars) |special| {
+                if (c == special) {
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+
+    pub fn isValidUnit(unit: []const u8) bool {
+        const all_units = [_][]const []const u8{
+            &LengthUnits, &AngleUnits, &TimeUnits, &FrequencyUnits, &ResolutionUnits,
+        };
+
+        for (all_units) |category| {
+            for (category) |valid_unit| {
+                if (std.mem.eql(u8, unit, valid_unit)) {
+                    return true;
+                }
+            }
+        }
+
+        return false;
+    }
+
+    pub fn startsWithFunction(value: []const u8) bool {
+        for (Functions) |func| {
+            if (value.len >= func.len + 1 and
+                std.mem.startsWith(u8, value, func) and
+                value[func.len] == '(')
+            {
+                return true;
+            }
+        }
+
+        return std.mem.indexOf(u8, value, "(") != null and
+            std.mem.indexOf(u8, value, ")") != null;
+    }
+};
diff --git a/src/browser/env.zig b/src/browser/env.zig
index e45ff75d..df747ac8 100644
--- a/src/browser/env.zig
+++ b/src/browser/env.zig
@@ -27,6 +27,7 @@ const WebApis = struct {
     pub const Interfaces = generate.Tuple(.{
         @import("crypto/crypto.zig").Crypto,
         @import("console/console.zig").Console,
+        @import("cssom/css_style_declaration.zig").Interfaces,
         @import("dom/dom.zig").Interfaces,
         @import("encoding/text_encoder.zig").Interfaces,
         @import("events/event.zig").Interfaces,
diff --git a/src/browser/html/elements.zig b/src/browser/html/elements.zig
index b5f62f8a..f34f8330 100644
--- a/src/browser/html/elements.zig
+++ b/src/browser/html/elements.zig
@@ -25,6 +25,8 @@ const URL = @import("../url/url.zig").URL;
 const Node = @import("../dom/node.zig").Node;
 const Element = @import("../dom/element.zig").Element;
 
+const CSSStyleDeclaration = @import("../cssom/css_style_declaration.zig").CSSStyleDeclaration;
+
 // HTMLElement interfaces
 pub const Interfaces = .{
     HTMLElement,
@@ -92,7 +94,6 @@ pub const Interfaces = .{
     HTMLTrackElement,
     HTMLUListElement,
     HTMLVideoElement,
-    CSSProperties,
 
     @import("form.zig").HTMLFormElement,
     @import("select.zig").HTMLSelectElement,
@@ -103,15 +104,19 @@ pub const Union = generate.Union(Interfaces);
 // Abstract class
 // --------------
 
-const CSSProperties = struct {};
-
 pub const HTMLElement = struct {
     pub const Self = parser.ElementHTML;
     pub const prototype = *Element;
     pub const subtype = .node;
 
-    pub fn get_style(_: *parser.ElementHTML) CSSProperties {
-        return .{};
+    style: CSSStyleDeclaration = .{
+        .store = .{},
+        .order = .{},
+    },
+
+    pub fn get_style(e: *parser.ElementHTML, state: *SessionState) !*CSSStyleDeclaration {
+        const self = try state.getNodeWrapper(HTMLElement, @ptrCast(e));
+        return &self.style;
     }
 
     pub fn get_innerText(e: *parser.ElementHTML) ![]const u8 {