CSS and JS updates, cache Synchronization Update Solution

Recently, when reading some websites, I found that all JS and CSS are marked with such a mark,

<LINK rel = "stylesheet" href = "http://static.ak.facebook.com/css/actionspro.css? 44: 72882 "type =" text/CSS "/>

 

Among them? What does it mean?

The value after the question mark can be treated as a version number. After the CSS file version is upgraded, in order to prevent page chaos caused by the cache file not synchronously updated in your browser, you can set this parameter. If the values are different, the browser will download the updated file.

The same is true for Js.