document.styleSheets(x).rules(y)

<script type="text/javascript">

function processStyles() {
	for (var i =  0 ; i < document.styleSheets.length; i++) {
		var sheet = document.styleSheets.item(i);
		if (sheet) {
			var rules;
			if (sheet.cssRules) {
				rules = sheet.cssRules;
			} else if (sheet.rules) {
				rules = sheet.rules;
			}
			if (rules) {
				for (var j =  0 ; j < rules.length; j++) {
					var name = rules.item(j).selectorText;
					// do something 
					// name: 'body', 'td', '.myClass', '#myId'
				}
			}
		}
	}
}


</script>