[doob]

The thing with both both css and javascript is that it can load one on top of another so as the browser is loading lines of code it could be feeding in a new css rule that over-rules another.

Also css is definintely browser specific so if you have 2 definitions of the same rule, but at different hierarchies in your css, then 1 would overrull the other. However, in this case, if the 2 rules were very similar, then one version might be compliant in IE and the other might not be, while both are complient with Firefox.

I'm surprised you can't identify what the div id or class for the banner ad is and what the image name is. Without that information, it would be impossible to try and diagnose the problem...