"Edit This Page" is an idea popularised if not conceived by
Dave Winer of
Userland Software.
The premise behind ETP is that the author/editor/contributor of a web page could call up a page in a web browser and immediately be able to edit it right in the browser - no ftp, no cut and paste, not much chance to stuff up. ETP could also allow external tools to hook into the web page working seamlessly with the web and making the idea of a file menu obselete.
Everything writeups are one implementation of ETP.