diff --git a/src/browser/js/ExecutionWorld.zig b/src/browser/js/ExecutionWorld.zig
index 77a5865d..e9a8786d 100644
--- a/src/browser/js/ExecutionWorld.zig
+++ b/src/browser/js/ExecutionWorld.zig
@@ -91,8 +91,7 @@ pub fn createContext(self: *ExecutionWorld, page: *Page, enter: bool, global_cal
         const global_template = js_global.getInstanceTemplate();
         global_template.setInternalFieldCount(1);
 
-        // Configure the missing property callback on the global
-        // object.
+        // Configure the missing property callback on the global object.
         if (global_callback != null) {
             const configuration = v8.NamedPropertyHandlerConfiguration{
                 .getter = struct {
@@ -162,15 +161,17 @@ pub fn createContext(self: *ExecutionWorld, page: *Page, enter: bool, global_cal
     }
     errdefer if (enter) handle_scope.?.deinit();
 
+    const js_global = v8_context.getGlobal();
     {
         // If we want to overwrite the built-in console, we have to
         // delete the built-in one.
-        const js_obj = v8_context.getGlobal();
+
         const console_key = v8.String.initUtf8(isolate, "console");
-        if (js_obj.deleteValue(v8_context, console_key) == false) {
+        if (js_global.deleteValue(v8_context, console_key) == false) {
             return error.ConsoleDeleteError;
         }
     }
+
     const context_id = env.context_id;
     env.context_id = context_id + 1;
 
@@ -195,17 +196,11 @@ pub fn createContext(self: *ExecutionWorld, page: *Page, enter: bool, global_cal
         v8_context.setEmbedderData(1, data);
     }
 
-    // @ZIGDOM
     // Custom exception
-    // NOTE: there is no way in v8 to subclass the Error built-in type
-    // TODO: this is an horrible hack
-    // inline for (JsApi) |JsApi| {
-    //     const Struct = s.defaultValue().?;
-    //     if (@hasDecl(Struct, "ErrorSet")) {
-    //         const script = comptime JsApi.Meta.name ++ ".prototype.__proto__ = Error.prototype";
-    //         _ = try context.exec(script, "errorSubclass");
-    //     }
-    // }
+    // TODO: this is an horrible hack, I can't figure out how to do this cleanly.
+    {
+        _ = try context.exec("DOMException.prototype.__proto__ = Error.prototype", "errorSubclass");
+    }
 
     try context.setupGlobal();
     return context;
diff --git a/src/browser/tests/document/query_selector.html b/src/browser/tests/document/query_selector.html
index bd4b0d57..b83c3928 100644
--- a/src/browser/tests/document/query_selector.html
+++ b/src/browser/tests/document/query_selector.html
@@ -23,7 +23,7 @@
 <main>Main content</main>
 
 <script id=byId name="test1">
-  testing.expectError("Syntax Error", () => document.querySelector(''));
+  testing.expectError("SyntaxError: Syntax Error", () => document.querySelector(''));
   testing.withError((err) => {
     testing.expectEqual(12, err.code);
     testing.expectEqual("SyntaxError", err.name);
diff --git a/src/browser/tests/document/query_selector_all.html b/src/browser/tests/document/query_selector_all.html
index e289b444..aa56b285 100644
--- a/src/browser/tests/document/query_selector_all.html
+++ b/src/browser/tests/document/query_selector_all.html
@@ -32,7 +32,7 @@
 </script>
 
 <script id=script1 name="test1">
-  testing.expectError("Syntax Error", () => document.querySelectorAll(''));
+  testing.expectError("SyntaxError: Syntax Error", () => document.querySelectorAll(''));
   testing.withError((err) => {
     testing.expectEqual(12, err.code);
     testing.expectEqual("SyntaxError", err.name);
diff --git a/src/browser/tests/domexception.html b/src/browser/tests/domexception.html
index 3f2825fd..1ed43e8d 100644
--- a/src/browser/tests/domexception.html
+++ b/src/browser/tests/domexception.html
@@ -120,16 +120,15 @@
 <div id="content">
   <a id="link" href="foo" class="ok">OK</a>
 </div>
-<!-- <script id=hierarchy_error>
+
+<script id=hierarchy_error>
   let link = $('#link');
   let content = $('#content');
 
   testing.withError((err) => {
-    const msg = "Failed to execute 'appendChild' on 'Node': The new child element contains the parent.";
     testing.expectEqual(3, err.code);
-    testing.expectEqual(msg, err.message);
-    testing.expectEqual('HierarchyRequestError: ' + msg, err.toString());
+    testing.expectEqual('Hierarchy Error', err.message);
     testing.expectEqual(true, err instanceof DOMException);
     testing.expectEqual(true, err instanceof Error);
   }, () => link.appendChild(content));
-</script> -->
+</script>
diff --git a/src/browser/tests/element/matches.html b/src/browser/tests/element/matches.html
index 324453cb..5e1721b5 100644
--- a/src/browser/tests/element/matches.html
+++ b/src/browser/tests/element/matches.html
@@ -66,7 +66,7 @@
 {
   const container = $('#test-container');
 
-  testing.expectError("Syntax Error", () => container.matches(''));
+  testing.expectError("SyntaxError: Syntax Error", () => container.matches(''));
   testing.withError((err) => {
     testing.expectEqual(12, err.code);
     testing.expectEqual("SyntaxError", err.name);
diff --git a/src/browser/tests/element/query_selector.html b/src/browser/tests/element/query_selector.html
index 9750bd1a..9564ca6d 100644
--- a/src/browser/tests/element/query_selector.html
+++ b/src/browser/tests/element/query_selector.html
@@ -12,7 +12,7 @@
   const p1 = $('#p1');
   testing.expectEqual(null, p1.querySelector('#p1'));
 
-  testing.expectError("Syntax Error", () => p1.querySelector(''));
+  testing.expectError("SyntaxError: Syntax Error", () => p1.querySelector(''));
   testing.withError((err) => {
     testing.expectEqual(12, err.code);
     testing.expectEqual("SyntaxError", err.name);
diff --git a/src/browser/tests/element/query_selector_all.html b/src/browser/tests/element/query_selector_all.html
index f203abe4..eeedc876 100644
--- a/src/browser/tests/element/query_selector_all.html
+++ b/src/browser/tests/element/query_selector_all.html
@@ -24,7 +24,7 @@
 <script id=errors>
 {
   const root = $('#root');
-  testing.expectError("Syntax Error", () => root.querySelectorAll(''));
+  testing.expectError("SyntaxError: Syntax Error", () => root.querySelectorAll(''));
   testing.withError((err) => {
     testing.expectEqual(12, err.code);
     testing.expectEqual("SyntaxError", err.name);
diff --git a/src/browser/tests/element/selector_invalid.html b/src/browser/tests/element/selector_invalid.html
index 826ce7b7..38c68671 100644
--- a/src/browser/tests/element/selector_invalid.html
+++ b/src/browser/tests/element/selector_invalid.html
@@ -45,8 +45,8 @@
     const container = $('#container');
 
     // Empty selectors
-    testing.expectError("Syntax Error", () => container.querySelector(''));
-    testing.expectError("Syntax Error", () => document.querySelectorAll(''));
+    testing.expectError("SyntaxError: Syntax Error", () => container.querySelector(''));
+    testing.expectError("SyntaxError: Syntax Error", () => document.querySelectorAll(''));
 }
 </script>
 
diff --git a/src/browser/tests/legacy/dom/exceptions.html b/src/browser/tests/legacy/dom/exceptions.html
index c6bb91f1..654f68ca 100644
--- a/src/browser/tests/legacy/dom/exceptions.html
+++ b/src/browser/tests/legacy/dom/exceptions.html
@@ -10,10 +10,9 @@
   let link = $('#link');
 
   testing.withError((err) => {
-    const msg = "Failed to execute 'appendChild' on 'Node': The new child element contains the parent.";
     testing.expectEqual(3, err.code);
-    testing.expectEqual(msg, err.message);
-    testing.expectEqual('HierarchyRequestError: ' + msg, err.toString());
+    testing.expectEqual('Hierarchy Error', err.message);
+    testing.expectEqual('HierarchyRequestError: Hierarchy Error', err.toString());
     testing.expectEqual(true, err instanceof DOMException);
     testing.expectEqual(true, err instanceof Error);
   }, () => link.appendChild(content));
diff --git a/src/browser/webapi/DOMException.zig b/src/browser/webapi/DOMException.zig
index f2558752..f392e676 100644
--- a/src/browser/webapi/DOMException.zig
+++ b/src/browser/webapi/DOMException.zig
@@ -23,16 +23,16 @@ const Page = @import("../Page.zig");
 const DOMException = @This();
 
 _code: Code = .none,
-_custom_message: ?[]const u8 = null,
 _custom_name: ?[]const u8 = null,
+_custom_message: ?[]const u8 = null,
 
 pub fn init(message: ?[]const u8, name: ?[]const u8) DOMException {
     // If name is provided, try to map it to a legacy code
     const code = if (name) |n| Code.fromName(n) else .none;
     return .{
         ._code = code,
-        ._custom_message = message,
         ._custom_name = name,
+        ._custom_message = message,
     };
 }
 
@@ -104,8 +104,8 @@ pub fn getMessage(self: *const DOMException) []const u8 {
     }
     return switch (self._code) {
         .none => "",
-        .invalid_character_error => "Error: Invalid Character",
-        .index_size_error => "IndexSizeError: Index or size is negative or greater than the allowed amount",
+        .invalid_character_error => "Invalid Character",
+        .index_size_error => "Index or size is negative or greater than the allowed amount",
         .syntax_error => "Syntax Error",
         .not_supported => "Not Supported",
         .not_found => "Not Found",
@@ -114,14 +114,17 @@ pub fn getMessage(self: *const DOMException) []const u8 {
     };
 }
 
-pub fn toString(self: *const DOMException) []const u8 {
-    if (self._custom_message) |msg| {
-        return msg;
-    }
-    return switch (self._code) {
-        .none => "Error",
-        else => self.getMessage(),
+pub fn toString(self: *const DOMException, page: *Page) ![]const u8 {
+    const msg = blk: {
+        if (self._custom_message) |msg| {
+            break :blk msg;
+        }
+        switch (self._code) {
+            .none => return "Error",
+            else => break :blk self.getMessage(),
+        }
     };
+    return std.fmt.bufPrint(&page.buf, "{s}: {s}", .{ self.getName(), msg }) catch return msg;
 }
 
 pub fn className(_: *const DOMException) []const u8 {
diff --git a/src/browser/webapi/Node.zig b/src/browser/webapi/Node.zig
index 1495cb09..41357bcc 100644
--- a/src/browser/webapi/Node.zig
+++ b/src/browser/webapi/Node.zig
@@ -190,12 +190,27 @@ pub fn parentElement(self: *const Node) ?*Element {
     return parent.is(Element);
 }
 
+// Validates that a node can be inserted as a child of parent.
+fn validateNodeInsertion(parent: *Node, node: *Node) !void {
+    // Check if parent is a valid type to have children
+    if (parent._type != .document and parent._type != .element and parent._type != .document_fragment) {
+        return error.HierarchyError;
+    }
+
+    // Check if node contains parent (would create a cycle)
+    if (node.contains(parent)) {
+        return error.HierarchyError;
+    }
+}
+
 pub fn appendChild(self: *Node, child: *Node, page: *Page) !*Node {
     if (child.is(DocumentFragment)) |_| {
         try page.appendAllChildren(child, self);
         return child;
     }
 
+    try validateNodeInsertion(self, child);
+
     page.domChanged();
 
     // If the child is currently connected, and if its new parent is connected,
@@ -435,6 +450,8 @@ pub fn insertBefore(self: *Node, new_node: *Node, ref_node_: ?*Node, page: *Page
         return new_node;
     }
 
+    try validateNodeInsertion(self, new_node);
+
     const child_already_connected = new_node.isConnected();
     // Check if we're adopting the node to a different document
     const child_root = new_node.getRootNode(null);
@@ -464,12 +481,8 @@ pub fn replaceChild(self: *Node, new_child: *Node, old_child: *Node, page: *Page
     if (old_child._parent == null or old_child._parent.? != self) {
         return error.HierarchyError;
     }
-    if (self._type != .document and self._type != .element) {
-        return error.HierarchyError;
-    }
-    if (new_child.contains(self)) {
-        return error.HierarchyError;
-    }
+
+    try validateNodeInsertion(self, new_child);
 
     _ = try self.insertBefore(new_child, old_child, page);
     page.removeNode(self, old_child, .{ .will_be_reconnected = false });
@@ -840,7 +853,7 @@ pub const JsApi = struct {
     pub const previousSibling = bridge.accessor(Node.previousSibling, null, .{});
     pub const parentNode = bridge.accessor(Node.parentNode, null, .{});
     pub const parentElement = bridge.accessor(Node.parentElement, null, .{});
-    pub const appendChild = bridge.function(Node.appendChild, .{});
+    pub const appendChild = bridge.function(Node.appendChild, .{ .dom_exception = true });
     pub const childNodes = bridge.accessor(Node.childNodes, null, .{});
     pub const isConnected = bridge.accessor(Node.isConnected, null, .{});
     pub const ownerDocument = bridge.accessor(Node.ownerDocument, null, .{});