Xena and Firefox, Opera, &c.
The current Xena Table of Contents uses a system called Deeptree to render layers of organized content and references a description page for each content item. It was written, I believe, in around 1997 and is largely unchanged from then. I think you can even look it up as a code sample on MSDN Online - for the time it was pretty slick. However, it uses DHTML to collapse the menu items, which was dropped by everyone but Microsoft when we *ahem* "extended" the standard. (As a disclaimer here, I won't publish any comments regarding the right or wrong of DHTML or Java support, both sides had their issues). When the site was designed, however, I don't believe anyone planned on this happening and so the site works fine for IE browsers, but pretty much tanks for anything else. The use of ActiveX to do checks and updates for File Transfer Manager is also a cross-browser issue, we handle it poorly today.
As we started work on Xena 3.0 about a year ago, one of my priority 1 requirements was to make the site fully cross-browser compatible. Funnily enough, the operations team (who tend to be pretty focused) told me that losing Deeptree wasn't required, because 99.5% of our client browsers were IE. I was able, however, to make the point that this could possibly be the case because we only support IE (after explaining that "support" is different from "can be accessed") and so that might possibly be a factor. The net-net of this is that cross-browser compatibility for Firefox, Opera, and IE will be included in the update for all major site functions.