<!DOCTYPE html>
<html>
<head>
<style>
div {
background-color: red;
}
div[mixedCase=true] {
background-color: green !important;
}
</style>
<script>
function f() {
var elem = document.createElement("div");
elem.setAttribute("mixedcase",true);
elem.appendChild(document.createTextNode("text"));
document.getElementsByTagName("body")[0].appendChild(elem); }
</script>
</head>
<body onload="f();">
</body>
</html>