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