CSS or JS file followed by parameters

Previously did not understand, see such as the CSS link above the site? v=20130203 like this

It was later discovered to be a way to prevent the browser from reading the cache by forcing the cache to flush.

"For example, Sina homepage in the April 5, 2010 revision, just change the CSS style sheet, can be behind the CSS, such as. css?2010.4.5, so that users do not clean the cache to open the Sina home page will not be the same as before, When the server reads the CSS file, it will re-read the latest 2010.4.5 "

CSS or JS file followed by parameters