According to a study by Aptiquant, a Canadian psychometric-assessment firm, users of Internet Explorer may have lower IQ levels than users of other browsers. The study also stated that Opera users tended to have the highest IQ levels of any other browser users.
Apparantly this test was a hoax, so if you happen to see it circulating around anywhere, don't believe it.
In my opinion, the people with the highest intelligence level are probably those who are completely independant of computers and web browsers and obtain their knowledge from books.
Then again, I could be wrong. I don't know.