Stupidflanders.org
Stupidflanders.org is a website that has humorous and/or embarrassing video clips of Ned Flanders, such as Ned doing a very unconvincing impression of a vampire: "Blaghhhh." It is likely that Homer is a regular contributor. He videos Ned doing something that he (Homer) considers to be silly and says he "can't wait to upload it to stupidflanders.org!"
It isn't known who actually owns the website. But because the name is stupidflanders.org and Homer has a habit of constantly referring to Ned as "Stupid Flanders," it is probable that Homer was at least involved in the site's creation. All the same, Homer never actually admits to owning the website; it could have been created by anyone in Springfield.
Behind the Scenes
There is no actual website named stupidflanders.org. However, in real life, Twentieth-Century Fox does own the domain name.
