diff --git a/src/browser/tests/css/stylesheet.html b/src/browser/tests/css/stylesheet.html
index 84e99658..7eab1a4e 100644
--- a/src/browser/tests/css/stylesheet.html
+++ b/src/browser/tests/css/stylesheet.html
@@ -436,6 +436,15 @@
 
     sheet.deleteRule(0);
     testing.expectEqual(0, sheet.cssRules.length);
+
+    let caught = false;
+    try {
+        sheet.deleteRule(5);
+    } catch (e) {
+        caught = true;
+        testing.expectEqual('IndexSizeError', e.name);
+    }
+    testing.expectTrue(caught);
 }
 </script>
 
diff --git a/src/browser/webapi/css/CSSRuleList.zig b/src/browser/webapi/css/CSSRuleList.zig
index e769bfbd..6c159aa2 100644
--- a/src/browser/webapi/css/CSSRuleList.zig
+++ b/src/browser/webapi/css/CSSRuleList.zig
@@ -24,14 +24,14 @@ pub fn item(self: *const CSSRuleList, index: usize) ?*CSSRule {
 
 pub fn insert(self: *CSSRuleList, index: u32, rule: *CSSRule, page: *Page) !void {
     if (index > self._rules.items.len) {
-        return error.IndexSizeError; // Or standard DOMException mapped error
+        return error.IndexSizeError;
     }
     try self._rules.insert(page.arena, index, rule);
 }
 
-pub fn remove(self: *CSSRuleList, index: u32) void {
+pub fn remove(self: *CSSRuleList, index: u32) !void {
     if (index >= self._rules.items.len) {
-        return; // Ignore or throw? Standard says IndexSizeError DOMException, but we might just no-op or return an error depending on the caller.
+        return error.IndexSizeError;
     }
     _ = self._rules.orderedRemove(index);
 }
diff --git a/src/browser/webapi/css/CSSStyleDeclaration.zig b/src/browser/webapi/css/CSSStyleDeclaration.zig
index c120f7b1..13499033 100644
--- a/src/browser/webapi/css/CSSStyleDeclaration.zig
+++ b/src/browser/webapi/css/CSSStyleDeclaration.zig
@@ -193,7 +193,6 @@ pub fn setCssText(self: *CSSStyleDeclaration, text: []const u8, page: *Page) !vo
     while (it.next()) |declaration| {
         try self.setPropertyImpl(declaration.name, declaration.value, declaration.important, page);
     }
-
     try self.syncStyleAttribute(page);
 }
 
diff --git a/src/browser/webapi/css/CSSStyleSheet.zig b/src/browser/webapi/css/CSSStyleSheet.zig
index 5ab48e77..70f9c2ad 100644
--- a/src/browser/webapi/css/CSSStyleSheet.zig
+++ b/src/browser/webapi/css/CSSStyleSheet.zig
@@ -73,7 +73,7 @@ pub fn insertRule(self: *CSSStyleSheet, rule: []const u8, index: u32, page: *Pag
 
 pub fn deleteRule(self: *CSSStyleSheet, index: u32, page: *Page) !void {
     const rules = try self.getCssRules(page);
-    rules.remove(index);
+    try rules.remove(index);
 }
 
 pub fn replace(self: *CSSStyleSheet, text: []const u8, page: *Page) !js.Promise {
@@ -116,8 +116,8 @@ pub const JsApi = struct {
     pub const disabled = bridge.accessor(CSSStyleSheet.getDisabled, CSSStyleSheet.setDisabled, .{});
     pub const cssRules = bridge.accessor(CSSStyleSheet.getCssRules, null, .{});
     pub const ownerRule = bridge.accessor(CSSStyleSheet.getOwnerRule, null, .{});
-    pub const insertRule = bridge.function(CSSStyleSheet.insertRule, .{});
-    pub const deleteRule = bridge.function(CSSStyleSheet.deleteRule, .{});
+    pub const insertRule = bridge.function(CSSStyleSheet.insertRule, .{ .dom_exception = true });
+    pub const deleteRule = bridge.function(CSSStyleSheet.deleteRule, .{ .dom_exception = true });
     pub const replace = bridge.function(CSSStyleSheet.replace, .{});
     pub const replaceSync = bridge.function(CSSStyleSheet.replaceSync, .{});
 };