The "Do Not Disturb" sign is off the door on the JKRowling website. This is where she announced the name of Harry Potter 6.
Here are some clues for finding her surprise. You get to the door by clicking on the ponytail holder in the middle of her desk. That takes you to the room. The Leaky Cauldron and Mugglenet websites posted the directions for getting to the "surprise."
The trick is finding the hidden light switch in the dark room. You have to click around, I would suggest, two thirds of the way down, slightly below the door handle, about one third across, from the left. You then have to hit the dart board with a particular number sequence,(the number of Dumbledore's high security vault at Gringrotts that held the Sorceror's stone, perhaps?) you can then enter a security code that you will find on the bulletin board in the "Extra Stuff" (tea cup) section of her website. It is on the business card for "Gobb lynn security" but you have to leave the window open for a while in order for a "visitor" to blow the other cards out of the way. You should do this first in order to get the number to the safe.
As I was writing this I had the vault window open and a "visitor" left a message on the mirror. This site is fun to explore. The FAQ section is very funny, there is some new stuff there. JKR's sense of humor comes through in her writing.