Contribute uses a system much like the Dreamweaver Check In/Check Out system to ensure that only one user at a time can edit a given web page. When you enable Contribute compatibility in Dreamweaver, the Dreamweaver Check In/Check Out system is automatically enabled.
To transfer files to and from a Contribute site using Dreamweaver, always use the Check In and Check Out commands. If you instead use the PUT and GET commands to transfer files, you might overwrite the modifications that a Contribute user has recently made to a file.
When you check a file in to a Contribute site, Dreamweaver makes a backup copy of the previous checked-in version of the file in the _baks folder and adds your user name and a date stamp to a Design Notes file.