When I saw many sites’ source code, parameters were passed to the linking file (CSS/JavaScript).
In the Stack Overflow source, I got
<script type="text/javascript" src="http://sstatic.net/js/master.js?v=55c7eccb8e19"></script>
Why is master.js?v=55c7eccb8e19 used?
I am sure that JavaScript/CSS files can’t get the parameters.
What is the reason?
It is usually done to prevent caching.
Let’s say you deploy version 2 of your new application and you want to cause the clients to refresh their CSS, you could add this extra parameter to indicate that it should re-request it from the server. Of course there are other approaches as well, but this is pretty simple.