title: How to temporarily add a CSS style?
body: <p>I have a <code>div</code> and when I mouse over it I want to change the background (and possibly other properties). I can do it by calling <code>el.style.backcolor = ""</code>, but is there a way I can add another CSS style to it then remove it later? Like <code>style += mouseOverStyle</code> and then <code>style -= mouseOverStyle</code>. That way I could select the properties to change in the CSS instead of in the JavaScript code.</p>
  
  <p>EDIT: I may want to apply the new style in other situations, not just mouseover, so #div:hover isn't really a general solution. What I'm really asking is is there something like style.add("style") and style.remove("style")?</p>