Ted Mosby is a jerk.com is a website created by one of Barney's one night stands (Anna) to whom he uses the line 'Ted Mosby, Architect'.
The site is first introduced in the episode The Bracket of season 3, where Barney is going to apologize to Anna, but instead continues to pretend he is Ted, telling every woman there to stay away from Ted Mosby and lock up their sisters and mothers. The real site also contains a 20 minute song performed by Charlene Amoia (who plays Wendy the Waitress), as Anna. A link to the real site can be found here.
Let it be noted that the girl who made the website thought Barney was Ted. Barney proved that the whole architect thing worked and slept with her. Then he snuck out when she was in the shower and left a note explaining that he was a ghost, although the prepared note used the name Barney Stinson. It can also be noted that the section "portraits of Ted" shows drawings of a man resembling Barney Stinson getting injured and or killed in several ways, Ted the Porn star, and a letter from Barney and the girl started it was from TED. So Ted Mosby actually isn't a jerk, after all, as shown at Ted Mosby is not a jerk.com