Why clearing or refreshing your cache?
Your browser has a folder in which certain items that have been downloaded are stored for future use. Graphic images (such as buttons and icons), photo's, and even entire web pages are examples of items which are saved or cached. When visiting a webpage your browser checks if a copy of the files on the page is in its cache already. If so, it will save the visitor some downloading and make webpages load faster. Some browsers refer to it's cach as Temporary Internet Files
There are some situtations when bypassing your browser's cache is prefered. Just clicking the refresh button (or hitting F5) won't be sufficient in this case, because this reloads the webpage while still using the old files from the cache. You need to refresh your cache first!
Click here for Chrome
Click here for Mozilla FireFox
Click here for Safari
Click here for Explorer