<!DOCTYPE html><html><head><metacharset="utf-8"/><title>Unique Identifier</title><linkrel="help"href="https://w3c.github.io/mathml-core/#attributes-common-to-html-and-mathml-elements"><linkrel="help"href="https://w3c.github.io/mathml-core/#css-styling"><linkrel="match"href="unique-identifier-3-ref.html"/><metaname="assert"content="Verify that the id attribute affects CSS selectors."><style>#fail{display:none;}#pass{background:green;}</style></head><body><p>Test passes if you see the text "PASS".</p><math><mtextid="fail"style="background: red; color: white;">FAIL</mtext><mtextid="pass"style="color: white;">PASS</mtext></math></body></html>