Ah, I've had this, with Safari. Guess which website causes the problem???
S'true. Every time I tried to get onto STW, after a minute or two, I just get the spinning beachball thing. Safari works fine, on every other website. So, I'm imagining a conflict between STW and my version of Safari. I've tried deleting the .plist, but this does not in any way make any difference.
I dunno. I use Firefox now, which is not as good as Safari, but works with STW.
I must point out, STW is the ONLY site that screws up Safari....
PS: You don't need to shut the whole computer down. You can Force Quit Safari.
Apple Logo (in top left hand corner)>Force Quit.