Where exactly to set cache expiration on css content?

Question

It seems that my browser checks for a new css on every request. Where and how do I indicate the time before checking for a new css?

Answer 1

Using IIS7 add a far future expires header or cache-control header by following the directions in this technet article.

I'm also a big fan of using the firefox plugin YSLOW for testing this and other performance features of web sites.