If you're using Iceweasel and Deviantart is throwing a bar up across the top that says you need to upgrade your browser to use the site, just install xul-ext-adblock-plus and create a new rule (Extensions > Filter preferences > Custom Filters > Actions > Show/Hide Filters > Add filter) then paste this line in:
deviantart.com#
#div[style*="updatebrowser_ylw_bg.png"]
Deviantart continues to work the same as always but you won't get that annoying bar that covers your messages and deviations and so on. You could just change your user-agent but perhaps if they see Iceweasel showing up in their visitor logs they might do something to fix that for all the other Iceweasel users. You could also just install Firefox but this is more fun.
Power to the people and so on.
Note: I recommend Adblock Plus instead of the forks because it still allows some ads to show and Deviantart *is* providing a nice service so I don't mind helping them pay for it. Except for the Flash ads. I always use Flashblock for those.