Browser support for these tags varies, but most browser makers seem to be adding support for them in their new and upcoming editions.
Browsers themselves have a number of processes to speed page delivery as well, such as DNS pre-resolve and TCP pre-connect. With DNS pre-resolve the browser can anticipate the domain name of the next site to be visited, through actions such as watching what letters a user starts typing in the navigation bar, or even by routinely fetching the IP addresses of that user's most visited Web sites.
A TCP pre-connect anticipates the user's next move through similar means. It "warms up" connections to sites, Soulders said, by opening ports and setting all the protocols in place for an eventual request.