I remember when I first saw amiga.org as it looks now, I remember thinking what great care and attention to detail had been taken in it's design. To this day the site has aged gracefully, and looks as good now as it always did.
Back then most sites worked in ibrowse.
But times change, software always needs updating and like the others have said it's only a matter of time until the script kiddies home in on you. Whilst I wouldn't like to see amiga.org go all "web 2.0" (I don't want to have to wait 20 seconds when I mouseover a menu i.e. ebay) I see no reason why it should not use an up-to-date markup.
There is no reason bash your head against a brick wall Wayne, make it so it's easy to apply updates and then focus on the sites content.
Trying to support browsers that can't support themselvs and are no good for anything else will just drain the life out of you that makes this place great. Don't get me wrong, my amiga is staying but the days I fire up ibrowse or aweb are gone as of a couple of years ago.