Basically, when StackOverflow goes offline, the server puts up a static webpage telling us all that it is down for maintenance.

Then, the server searches through its database and absorbs some of the awesomeness that [Jon Skeet][1] has rubbed off on the website and uses it to make changes that benefit the website. 

The problem is, too much of a good thing can be bad. So just before the server absorbs too much of Jon's awesomeness, it stops and comes back online. It will then repeat this process a week or two later.


  [1]: http://meta.stackoverflow.com/users/22656/jon-skeet