I checked again, definately cannot see it on mine. Seeing as this problem is only on web pages and not anything else, I would suggest a software problem, not hardware.
However, 58C is a bit high for just web browsing (were you just playing a game?). I get about 45C when browsing... but then again, I have the back of my lappy elevated (using a bottlecap under each of the back rubber feet), and I have custom settings.
To see, Elevate the back of your lappy, now go into the fanGUI options and under CPU temp control select the "normal" profile. Change the last box (fan 2) in the first fan level onto Fast... leave everything else the same. Now OK out of there, tick the enable temperature control and select the "normal" profile. See what you browsing temps are after a while now.... if its still that high, well I dunno, maybe its normal for others but not for mine!
Also, what web browser are you using? Have you changed any settings recently? Give another browser a whirl to see if the problem persists on those sites. Mozilla Firfox
is a good alternative.
It could just be a probem with IE or what ever you are using, this is what I suspect as it doesn't happen anywhere else.