Part of it is the large number of css and javascript files they load on each page. Visiting the home page (and not logged in) results in 34 http requests. Rou

Part of it is the large number of css and javascript files they load on each page. Visiting the home page (and not logged in) results in 34 http requests. Roughly 1/3 are images, and the rest are javascript and css. That many requests slows down all page loading, even when locally cached. If I were facebook (the best I have is a parody site of facebook: http://farcebook.codeirony.com/ http://farcebook.codeirony.com/), I would put all the css into 1 file, and all the js into 1 file. The other part is that they have a ton of users. It's a non trivial problem to make pages load quickly while providing dynamic content for millions of users.