JimH - it's probably obvious from my comments that I deal with browser issues on a regular basis, so I should note that I am completely sympathetic. There can be no doubt that for Windows-only programs, IE present features and opportunities not availalable elsewhere. Despite the above emoticon, I do understand.
IE is certainly the most prevalent browser. Each webmaster has to decide where their site's cutoff will be - platform, browser make, version, etc. I've left a quick thought about the methods of calculating browser popularity at the bottom of this too-long message.
As to other browsers adhering, that assumes that IE's processes and methods are 1)freely available for replication and 2)agreeably the best possible choices available. IMO, neither case is true.
As to the Flash thing, there's an option to show an image if Flash is not detected, using document.write. One can edit this and put almost any arbitrary HMTL in place. Even a GIF with an image-map might be better than no navigation at all. It's just a drop-down menu system
Sidenote: If/when you guys start looking at other msg boards, you might want to take a look at Invision Board
http://www.invisionboard.com*With regard to IE domination as represented in website statistics, I do think there's some unintentional misrepresentation. Stats are calculated partially by the number of pages served and to which browser. If a given site is not coded so as to be navigable or legible by other browsers, many users of those browsers will just leave, having seen only one page. Those with IE are more likely to browse/navigate further through the site, increasing the count. So IE percentages are raised by 'virtue' of site incompatibility, not necessarily by usage.
I pheel better now.