Why is Yslow telling me Use cookie-free domains on only one of my sites?

Question

I have Four websites all hosted under the same account (all under public_html of a main domain). All but one give me an A for "use cookie-free domains" but one of them gives me an F. What should I be doing to change this one domain? I don't even know what to look for...

Wait a second...grr...I just ran the test again, and got an A-weird...

Answer 1

From Yahoo performance rules:

You should make sure static components are requested with cookie-free requests.

Do you have static or dynamic site with "F" rating for cookie-free rule? This can also be triggered by large cookies, I think.