To completely purge your browser files I would recommend a handy little utility called CCleaner.
http://www.ccleaner.com/
Removes temporary files, cookies, URL history, autocomplete information, index.dat files, etc.
Works with Internet Explorer, Firefox and Opera (no Safari version).
It is free. Alternatively, you can obtain another free utility from the Major Geeks website called Dial-A-Fix that purges browser files.