Hello, I am developing a CMS and I would like to be able when a user is
editing a page to inform any other user that the page is being edited by
User X . Ofcourse that's not so difficult if you set a flag in the database
for example that the current document is being edited, and remove the flag
when the user saves the document and exits.

BUT what happens if user exits the editing page without folowing any link or
submit button that I can control. What happens if his computer
restarts/crashes or he kills the browser.

Database will have the document flaged as being edited by User X.

Do you know any good way of avoiding that problem or if you don't already
know, can you think of something similar ?

Thanks Angelos.