What browser are you using?
For IE7, you could try going to "tools" > "internet options", a dialog will pop up displaying the first ("general") tab. There, click on "delete" under the "browsing history" bit. A new dialog will pop up, allowing you to delete several things (temp files, cookies, etc.). At least delete the first 2, but it wouldn't hurt much to just click "delete all".
You could also go to the last tab ("advanced") and click the "reset" button at the bottom.
> you should only use this if your browser is in an unusable state <
I'm not an expert, read the information the pages display and use your head. If you don't trust it, don't do it.
Hope it helps.