I recently completed a fairly small job which should have been straightforward, but which took a lot longer than I wanted it to because the client uses NS4, and out of some masochistic aspiration to professionalism I set out to write a site that would look good, and more-or-less the same, in NS4, NS6+ and IE5. It was more of a pain in the neck than I thought, particularly because I like CSS. I was working with a pretty standard format for each page in the site, though.
in reply to OT: Web Design - Catering to Everyone
A thing I thought of doing, but too late for it to make sense to change horses midstream, was to have two or more sites, and a js browser-sniffer to send users to the right one. That would have been great because then I could have optimised the design for each individual browser - as it is, different aspects look not quite right depending on your platform. This would also have been a good fit because the content site (http://www.cookeassociates.com) gets managed through a MySQL db (which, as well as backing up, generates the content tree you see on each page), so it would have been easy to output the site through several different templates, one per browser. Maybe next time...
§ George Sherston