Have a couple of questions regarding my XHTML markup.

For CSS is it better to use

Code:
<link rel="stylesheet" href="/css/mystyle.css">
or

Code:
<link rel="stylesheet" href="http://www.mysite.com/css/mystyle.css">
With Javascript the same question, is it better to use

Code:
<script src="/js/theme.js"></script>
or

Code:
<script src="http://www.mysite.com/js/theme.js"></script>
Finding some people are complaining my site loads slow and I have notice it on older versions of IE