lock web page when editing

hi just seeing how everyone would approach this problem. i'm building a content management system and many people can edit a web page. if someone clicks on "edit" for a web page then i want to lock that page and not allow anyone else to "edit" the same page until the first person is done. how would i be able to tell if that first person is still editing or they have left??? if they close the browser then the web page would be locked forever. how do i get around that? _________________________________________________________ Do You Yahoo!? Get your free @yahoo.com address at http://mail.yahoo.com