CSS files should be refreshed every time you start your app. Most problems appear with JavaScript calls. To solve that: In your tag, add a parameter with a timestamp in your programming language, for example with php:
<script type="text/javascript" src="javacsript.js?v=<?php echo time(); ?>"></script>
That worked for me. If you still have problems with your CSS files, try to do the same with those tags:
<link rel="stylesheet" href="stylesheet.css?v=<?php echo time(); ?>" />
I haven't tried this one though.