Upgrade to IE 5!
So I'm registering for the SAT and I'm greeted with this incredibly helpful message:
Right....because IE 5, Netscape 6.2, and AOL 5 really exist for Linux and are obviously far more advanced than Opera 9.
Since they give an option "Continue with current browser", no WTF. Though "Your browser appears to not be one we have tested" might be a better wording.
you can always tell Opera to emulate IE or whatever (well, not really emulate, but send that as it's User Agent...)