Google has added "pre-fetching" for the top result on your searches. This means that when you google for something, the top link is automatically loaded in the background in your browser (this only works for Firefox/Mozilla) so that if you click it, it appears immediately, with no network lag.
(via /.)
Update: Kwai Chang Caine sez, "the prefetched site gets to set all it's cookies without you knowing (unless your browser is configured to tell you about cookies). Presumably this includes any third party inclusions in the target page."
