You can decrease request latency by serving static resources from a domain that doesn't serve cookies. This technique is especially useful for pages referencing large volumes of rarely cached static content, such as frequently changing image thumbnails, or infrequently accessed image archives. We recommend this technique for any page that serves more than 5 static resources. 

 

 

Keep alive is a method to allow the same tcp connection for HTTP conversation instead of opening a new one with each new request. More simply put, it is a communication between the web server and the web browser that says