We can add into references to JS or CSS files from HTML:
The attribute does nothing other than trick the browser into thinking that the .js file must be retrieved from server for new version instead of cached .
You can write your own AssemblyVersionNumber() function or use my function from My SystemHelper class. like the following:
Idea from http://www.thescripts.com/forum/thread165240.html
Note that it could be problems, if head element has runat="server" attribute.
Also consider to reduce number of CSS and JS files.