Google does stores a copy of webpage as it crawls the web for back-up uses it when a webpage is not available which is called as Google cached page, Google uses this cached content to judge the match for query. Before launch of Instant Previews “cached”  and “similar” links displayed near the URL in search results, this is not the case after launch of Instant Previews they’ve been moved to Instant Preview section.

cached and similar links in Google

finding similar and cached links in Google Search results

When you perform a search in Google, simply hover the mouse over the search result,  a little bar with arrow appear wait for a second for preview page to shown on right, there you’ll find Cached link.

Note : You can also use Cache: Operator to access Google cached page of a site, for e.g query shows last indexed version of Google homepage with the info about the date the cache was created. You can also view text -version of cached page by clicking  “Text -only version link”.

Similarly you can use related : Operator to find the sites similar to the site you’ve queried for. [Via]