This blog reported on July 7 that the Lonelygirl15 and Katemodern websites on lg15.com had been down and were still not back up. Lonelygirl15 Creator Miles Beckett commented on July 8 that they were "looking into this."
At this point, the sites have been down so long that if you google "lonelygirl15", the hit for lg15.com previews the wordpress errors that you see when you try to visit either http://www.lg15.com/lonelygirl15 or http://www.lg15.com/katemodern.
Hopefully the sites will return soon, but its unclear why they've been down for so long.
The 436 was not immediately available for comment.
ETA 9:45pm PDT: Thanks to Mathieas for providing this handy counter for keeping track of how many days the Creators have been "looking into this":