Whats is a browser 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), photos, 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 cache as Temporary Internet Files.
Why do I need to do this?
When you log into sites like Facebook or Gmail, YouTube etc. your session data is often kept in your browser’s cache, so anyone who has access to your computer can access your secure account information, unless you manually log out of all these sites. To log out of all at once simply clear your browser cache, rather than signing out of each individually.
Also some sites save their entire pages as cached data, and you may not be seeing the latest content they have available, so its a good idea to clear your cache periodically so that you have access to the latest data from their servers. This is particularly useful if you are making updates to your managed web pages but are not yet seeing them.
Corrupt sessions data may also cause you to have problems logging into some secure sites. Magento admin user may find this to be true when trying to login to the Magento admin panel.
Ok, so how is it done?
Most browsers have use a handy little short cut: Ctrl + Shift + Del which should open up your browsers cache dialog box. If that does not work for you the folks at refreshyourcache.com have prepared a great photo and video guide for all the most popular browsers used today. They also keep the instructions fairly updated so no matter what browser you use, step by step instructions are there for you.