Q:

Ensuring Updated CSS/JavaScript on Client Side

I'm trying to ensure that visitors of my ASP.NET MVC website always have the most-current CSS and Javascript (and not some older cached version).
I tried to realize this by generating a seed value when the application domain starts, and automatically append it to the CSS and Javascript URLs (so now instead of /Content/All.js the link is /Content/All.js?549238 etc.).
Unfortunately I just found out by debugging via Firebug that this causes now a full download request every time (the new "seeded" response is no longer cached at all, but I only wanted the first check to download the 'updated' version, but then cache again/only check if there is a difference). 
How can I achieve my goal, is there a better way of doing this? I need the client to always request the newest version, but then cache if no change happened.
Edit: This appears to be related to the fact that my page is served over SSL. I  asked a follow up question here regarding enabling clientside caching with SSL.

A:

I think the seed value you are generating is a random number. Replace this with  a version number so that it will be re downloaded only when the version number of your application changes.
Like
/Content/All.js?appVer1.5
and when you modify the application you can change that to something like
/Content/All.js?appVer1.6

