Using Javascript in CSS
HTC with IE body { behavior:url(script.htc); } script.htc XBL with Firefox body { -moz-binding: url(script.xml#mycode); } script.xml: alert("XBL script executed."); I think what you may be thinking of is expressions or "dynamic properties", which are only supported by IE and let you set a property to the result of a javascript expression. Example: width:expression(document.body.clientWidth > 800? "800px": "auto" ); detail here: http://stackoverflow.com/questions/476276/using-javascript-in-css