<!DOCTYPE html> <style> div { color: green; } div#reverse { color: red; } </style> <div id="null" style="color: red">This text should be green</div> <div id="emptystring"style="color: red">This text should be green</div> <div id="reverse" style="color: green">This text should be green</div> <script> document.getElementById("null").style.color = null; document.getElementById("emptystring").style.color = ""; document.getElementById("reverse").style.color = "some invalid color string"; </script>