This depends fully on what the computer is doing. Even what website makes a difference.
For instance(i5 750), on this forum(this exact page with HWmon + winamp playing). 2-4% on the main Toms page 9-12%
Also note that with add block, the load may be lighter as well.
Unless you run into issues, I would not worry about it.
Even video card clocks change on different websites since the web browser can use the video card for acceleration.
Tom's I have no clue WHY it stays that high, but with that card, it did. Newer cards do not seem to get stuck or even have to clock up like thathttp://imageshack.us/a/img209/4765/tomshardwaregpu.jpg