Google saves a copy of each page it examines and caches it.

This especially comes in handy if you’re looking for a Web site that is no longer there (for whatever reason), or if the Web site you’re looking for is down due to an unusually high volume of traffic.

To access the cached copy of a website use the below syntax

cache:http://yassershaikh.com

I normally use it to get back an orignal copy of a website/page I have edited without taking a proper backup. ;)