Serving static content from a cookieless domain

[symkat]

Using another domain to serve static content also speeds up the rendering by getting around the concurrent-connections to each domain rule in the browsers.

If you're using a sub-domain of the main domain chances are this will not help with cookies. In the case of your main content being on example.com and then using the sub-domain static.example.com cookies will generally be set for .example.com and thus be sent with requests to static.example.time. This is particularly true with Google AdSense which doesn't allow you to limit the domain the cookie is set for.

I wrote an article about this subject, including speed tests with Chrome and Keynote for the before and after: http://symkat.com/105/cookieless-domains/

I hope this is helpful.