diff --git a/Libraries/LibWeb/DOM/Element.cpp b/Libraries/LibWeb/DOM/Element.cpp
index 50f0f89bbed..65496f8d492 100644
--- a/Libraries/LibWeb/DOM/Element.cpp
+++ b/Libraries/LibWeb/DOM/Element.cpp
@@ -3252,7 +3252,7 @@ size_t Element::ordinal_value() const
     auto reversed = false;
     if (is<HTML::HTMLOListElement>(owner)) {
         auto const* ol_element = static_cast<const HTML::HTMLOListElement*>(owner);
-        numbering = ol_element->starting_value();
+        numbering = ol_element->starting_value().value();
         reversed = ol_element->has_attribute(HTML::AttributeNames::reversed);
     }
 
diff --git a/Libraries/LibWeb/DOM/Node.h b/Libraries/LibWeb/DOM/Node.h
index 3a76ac86ad7..4b7cbb206b9 100644
--- a/Libraries/LibWeb/DOM/Node.h
+++ b/Libraries/LibWeb/DOM/Node.h
@@ -214,6 +214,14 @@ public:
     virtual bool is_html_span_element() const { return false; }
     virtual bool is_html_frameset_element() const { return false; }
     virtual bool is_html_fieldset_element() const { return false; }
+    virtual bool is_html_li_element() const { return false; }
+    virtual bool is_html_menu_element() const { return false; }
+    virtual bool is_html_olist_element() const { return false; }
+    virtual bool is_html_ulist_element() const { return false; }
+    ALWAYS_INLINE bool is_html_ol_ul_menu_element() const
+    {
+        return is_html_olist_element() || is_html_ulist_element() || is_html_menu_element();
+    }
     virtual bool is_navigable_container() const { return false; }
     virtual bool is_lazy_loading() const { return false; }
 
diff --git a/Libraries/LibWeb/HTML/HTMLLIElement.h b/Libraries/LibWeb/HTML/HTMLLIElement.h
index e07301fe409..f6bdf6a53df 100644
--- a/Libraries/LibWeb/HTML/HTMLLIElement.h
+++ b/Libraries/LibWeb/HTML/HTMLLIElement.h
@@ -41,6 +41,8 @@ public:
         MUST(set_attribute(AttributeNames::value, String::number(value)));
     }
 
+    virtual bool is_html_li_element() const override { return true; }
+
 private:
     HTMLLIElement(DOM::Document&, DOM::QualifiedName);
 
@@ -52,3 +54,10 @@ private:
 };
 
 }
+
+namespace Web::DOM {
+
+template<>
+inline bool Node::fast_is<Web::HTML::HTMLLIElement>() const { return is_html_li_element(); }
+
+}
diff --git a/Libraries/LibWeb/HTML/HTMLMenuElement.h b/Libraries/LibWeb/HTML/HTMLMenuElement.h
index e9c21ab25f9..4d44bf669d3 100644
--- a/Libraries/LibWeb/HTML/HTMLMenuElement.h
+++ b/Libraries/LibWeb/HTML/HTMLMenuElement.h
@@ -21,6 +21,8 @@ public:
     // https://www.w3.org/TR/html-aria/#el-menu
     virtual Optional<ARIA::Role> default_role() const override { return ARIA::Role::list; }
 
+    virtual bool is_html_menu_element() const override { return true; }
+
 private:
     HTMLMenuElement(DOM::Document&, DOM::QualifiedName);
 
@@ -28,3 +30,10 @@ private:
 };
 
 }
+
+namespace Web::DOM {
+
+template<>
+inline bool Node::fast_is<Web::HTML::HTMLMenuElement>() const { return is_html_menu_element(); }
+
+}
diff --git a/Libraries/LibWeb/HTML/HTMLOListElement.cpp b/Libraries/LibWeb/HTML/HTMLOListElement.cpp
index e0c51e4d98b..97adbffbfab 100644
--- a/Libraries/LibWeb/HTML/HTMLOListElement.cpp
+++ b/Libraries/LibWeb/HTML/HTMLOListElement.cpp
@@ -11,6 +11,7 @@
 #include <LibWeb/HTML/AttributeNames.h>
 #include <LibWeb/HTML/HTMLOListElement.h>
 #include <LibWeb/HTML/Numbers.h>
+#include <LibWeb/WebIDL/Types.h>
 
 namespace Web::HTML {
 
@@ -49,7 +50,7 @@ WebIDL::Long HTMLOListElement::start()
 }
 
 // https://html.spec.whatwg.org/multipage/grouping-content.html#concept-ol-start
-size_t HTMLOListElement::starting_value() const
+AK::Checked<i32> HTMLOListElement::starting_value() const
 {
     // 1. If the ol element has a start attribute, then:
     auto start = get_attribute(AttributeNames::start);
@@ -61,10 +62,11 @@ size_t HTMLOListElement::starting_value() const
         if (parsed.has_value())
             return parsed.value();
     }
-
     // 2. If the ol element has a reversed attribute, then return the number of owned li elements.
     if (has_attribute(AttributeNames::reversed)) {
-        return number_of_owned_list_items();
+        auto const reverse_list_starting_value = number_of_owned_list_items();
+        VERIFY(reverse_list_starting_value <= NumericLimits<WebIDL::Long>::max());
+        return reverse_list_starting_value;
     }
 
     // 3. Return 1.
diff --git a/Libraries/LibWeb/HTML/HTMLOListElement.h b/Libraries/LibWeb/HTML/HTMLOListElement.h
index 7687efeeefc..b7a002e8504 100644
--- a/Libraries/LibWeb/HTML/HTMLOListElement.h
+++ b/Libraries/LibWeb/HTML/HTMLOListElement.h
@@ -6,6 +6,7 @@
 
 #pragma once
 
+#include <AK/Checked.h>
 #include <LibWeb/ARIA/Roles.h>
 #include <LibWeb/HTML/HTMLElement.h>
 #include <LibWeb/WebIDL/Types.h>
@@ -28,7 +29,9 @@ public:
         MUST(set_attribute(AttributeNames::start, String::number(start)));
     }
 
-    size_t starting_value() const;
+    AK::Checked<i32> starting_value() const;
+
+    virtual bool is_html_olist_element() const override { return true; }
 
 private:
     HTMLOListElement(DOM::Document&, DOM::QualifiedName);
@@ -41,3 +44,10 @@ private:
 };
 
 }
+
+namespace Web::DOM {
+
+template<>
+inline bool Node::fast_is<Web::HTML::HTMLOListElement>() const { return is_html_olist_element(); }
+
+}
diff --git a/Libraries/LibWeb/HTML/HTMLUListElement.h b/Libraries/LibWeb/HTML/HTMLUListElement.h
index d1b92a1c09a..b3703d2a5d0 100644
--- a/Libraries/LibWeb/HTML/HTMLUListElement.h
+++ b/Libraries/LibWeb/HTML/HTMLUListElement.h
@@ -21,6 +21,8 @@ public:
     // https://www.w3.org/TR/html-aria/#el-ul
     virtual Optional<ARIA::Role> default_role() const override { return ARIA::Role::list; }
 
+    virtual bool is_html_ulist_element() const override { return true; }
+
 private:
     HTMLUListElement(DOM::Document&, DOM::QualifiedName);
 
@@ -31,3 +33,10 @@ private:
 };
 
 }
+
+namespace Web::DOM {
+
+template<>
+inline bool Node::fast_is<Web::HTML::HTMLUListElement>() const { return is_html_ulist_element(); }
+
+}