Конечно можно. Вот один из вариантов:
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN">
<html><head><title>New</title>
<script type="text/javascript">
window.onload = function(){
var style = document.createElement('style');
style.type = 'text/css';
var h = '#some:hover{color:#f00}';
var hover = document.createTextNode(h);
var head = document.getElementsByTagName('head')[0];
style.appendChild(hover);
head.appendChild(style);
}
</script>
</head><body>
<h1><a id="some" href="#">test</a></h1>
</body></html>