Your web browser caches (keeps local copies on your hard drive of) many of the pages and graphics it downloads as you are browsing the Web. This makes it faster to reload the same page when you return to it later. However, there is a risk that the cached information will be out of date, and sometimes the cached data becomes corrupted, so it is sometimes useful to clear out the browser cache. If you are having trouble loading a website, then this would be a first step in troubleshooting.
Firefox:
Click on the Firefox menu > History > Clear recent history… > Details > select Cache files (and uncheck the other history files if you don’t want to delete those).
Firefox earlier versions www.bnl.gov/itd/webapps/browsercache.asp#FireWin
Chrome:
Click on the “Wrench” symbol in the menubar (the Tools menu) > Settings > Under the Hood > in the Privacy section click Clear browsing data… and select which types of data that you want to clear (Cookies, cache, history, etc.)
(Older versions may have Options rather than Settings)
support.google.com/chrome/bin/answer.py?hl=en&answer=95582
Safari:
Click on the Safari menu > Reset Safari > select the items you want to clear, click Reset. (“Remove all website data” deletes both cookies and cache files).
www.bnl.gov/itd/webapps/browsercache.asp#Safari4
Safari on iPad: browsers.about.com/od/howtousemobilebrowser1/ss/safari-ipad-clear-cache.htm
Internet Explorer: www.bnl.gov/itd/webapps/browsercache.asp#IE9
Other programs use caches as well. For Windows there is a program CCleaner www.piriform.com/ccleaner which will clean out internet caches and a variety of other temporary and unneeded files as well.