Changing And Refreshing Div Content

I have a website with some navigation buttons on top. When one button is clicked I replace it's content with the content of a red button using this code:

document.getElementById('button').innerHTML = '
<a href="javascript:void(0)">
<img src="header/button_active.jpg" border="0" />
</a>'
The original code was enclosed in a DIV and I cant just change the img src because the original code is:

<div id="aanbiedingen">
<a href="javascript:void(0)">
<img src="1px_tranceparent.gif" name="Aanbiedingen" width="99px" height="20px" border="0" />
</a>
</div>

But when the orignal button is clicked, a ajax event goes off and loads the new page without reloading the button.
Using this code a button becomkes red once you click it. This is what I want.

Just one problem: when I click on another button, the first one stays red because it doesn't reload the page. Now I thought, I'll refresh the navigation page using a div and ajax. Code: