Internet Explorer & Mozilla / Firefox: what's different

Migrate apps from Internet Explorer to Mozilla

This article covered common issues web application developers face when they try to get their applications to work in Mozilla-based browsers. When you develop web applications, always consider possible browser differences and be informed about them. In Resources, you'll find two good references that provide in-depth coverage on cross-browser development. Following those guidelines not only allow your web applications to work in other browsers, but also on other platforms.

I haven't dealt with this sort of detail in years, but I can still follow it. This is the most succinct and useful discussion of the 2005 state of the browesr I've seen. IE is darned ugly.