diff --git a/Userland/Libraries/LibWeb/CSS/GeneralEnclosed.h b/Userland/Libraries/LibWeb/CSS/GeneralEnclosed.h
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+++ b/Userland/Libraries/LibWeb/CSS/GeneralEnclosed.h
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+/*
+ * Copyright (c) 2021, Sam Atkins <atkinssj@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/String.h>
+
+namespace Web::CSS {
+
+// Corresponds to Kleene 3-valued logic.
+// https://www.w3.org/TR/mediaqueries-4/#evaluating
+enum class MatchResult {
+    False,
+    True,
+    Unknown,
+};
+
+inline MatchResult as_match_result(bool value)
+{
+    return value ? MatchResult::True : MatchResult::False;
+}
+
+inline MatchResult negate(MatchResult value)
+{
+    switch (value) {
+    case MatchResult::False:
+        return MatchResult::True;
+    case MatchResult::True:
+        return MatchResult::False;
+    case MatchResult::Unknown:
+        return MatchResult::Unknown;
+    }
+    VERIFY_NOT_REACHED();
+}
+
+template<typename Collection, typename Evaluate>
+inline MatchResult evaluate_and(Collection& collection, Evaluate evaluate)
+{
+    size_t true_results = 0;
+    for (auto& item : collection) {
+        auto item_match = evaluate(item);
+        if (item_match == MatchResult::False)
+            return MatchResult::False;
+        if (item_match == MatchResult::True)
+            true_results++;
+    }
+    if (true_results == collection.size())
+        return MatchResult::True;
+    return MatchResult::Unknown;
+}
+
+template<typename Collection, typename Evaluate>
+inline MatchResult evaluate_or(Collection& collection, Evaluate evaluate)
+{
+    size_t false_results = 0;
+    for (auto& item : collection) {
+        auto item_match = evaluate(item);
+        if (item_match == MatchResult::True)
+            return MatchResult::True;
+        if (item_match == MatchResult::False)
+            false_results++;
+    }
+    if (false_results == collection.size())
+        return MatchResult::False;
+    return MatchResult::Unknown;
+}
+
+// https://www.w3.org/TR/mediaqueries-4/#typedef-general-enclosed
+class GeneralEnclosed {
+public:
+    GeneralEnclosed(String serialized_contents)
+        : m_serialized_contents(move(serialized_contents))
+    {
+    }
+
+    MatchResult evaluate() const { return MatchResult::Unknown; }
+    StringView to_string() const { return m_serialized_contents.view(); }
+
+private:
+    String m_serialized_contents;
+};
+}