css « function « Javascript Data Type Q&A

1. How can i make these functions use variables for the id? I cant the setTimeout to work when I do    stackoverflow.com

<script type="text/javascript">

  function changeBarAWidth(){

                 var bar = document.getElementById('firstbar');   
    ...

2. Passing HTML and CSS to Javascript    stackoverflow.com

I need to find a way to pass the visible div to javascript. This may not even be the best way to accomplish what I'm trying to accomplish, so I'm open ...