It's just a silly workaround for lagging links to inform users that something is really on going..
##Background Idea from Steve Souders' The Perception of Speed blogpost.
Keeping the old page in place improves the user experience for the same reason that making airline passengers walk six times longer to get their bags reduces complaints about long waits at the baggage claim. "Occupied time (walking to baggage claim) feels shorter than unoccupied time (standing at the carousel)," according to M.I.T. operations researcher Richard Larson, an expert on queueing. In my example of clicking a link, occupied time (looking at the old page) feels shorter than unoccupied time (staring at a blank screen).
Customize it according your needs. You can replace that ugly red bar with a cute, sparkling animgif loader or with a rolling bear head. Whatever.
Chrome, Firefox, Safari, IE things
http://dev3.zsitro.com/occupied.js/example/
Gabor Zsoter’s occupied.js is a great example of how the perception can be completely changed by just a small visual distraction. — Grahame Scott-Douglas