Need help regarding "Serving static content of a domain without cookies"

I just installed Google's "Page Speed" browser add-on that works with the "FireBug" plugin.

When I open my site www.decentbanners.com, FireBug scans the performance of the site, shows the result and also suggests what steps should be taken to increase the loading speed of the site.

One of the suggestions he is showing is

"Serve static content of a domain without cookies"

He is saying

Need help regarding "Serving static content of a domain without cookies"