1) Force Refresh
Depending on your operating system all you need to do is the following key combination:
Windows: ctrl + F5
Mac/Apple: Apple + R or command + R
2) Clearing Cache Memory
To ensure you see the latest version of a site you need to clear the cache memory. This is done by doing a force refresh by pressing both control and F5 buttons simultaneously on your keyboard (depending on your browser). Most times a simple force cache refresh won't work and you need to clear the cache by hand. On this site you can find step by step guides for Chrome, Firefox, Internet Explorer, Safari and more on how to refresh your cache.