What is a cache and why should I clear it?
When you access a website it will save or cache certain items onto your computer so that next time you visit, it will load faster. This includes graphic images (e.g. buttons and icons), photos and even entire web pages. These are also referred to as temporary internet files.
While this is great, sometimes the files saved get updated and you need the new files.
So you should clear your web browser's cache periodically in order to prevent or resolve performance problems. Clear your browser's cache will force it to download all latest data from a website!
This page by the University of Wisconsin-Madison contains instructions on how to clear the cache for many different web browsers.