Just had a problem with a website which worked fine in IE, however when viewed in Firefox, some of the <A HREF> links weren’t working!
Turns out it was a problem with the z-axis. One of the other elements on the page was appearing on top of the links and obscuring them. By using “z-index” I was able to re-order the elements, bringing the links to the surface again – and all worked fine again.
Here’s a good description of how to use z-index:
https://developer.mozilla.org/en/Understanding_CSS_z-index/Adding_z-index