If you are working on a project with someone else, whether it’s doing web development or something else, using a revision control system, such as subversion or CVS, will save you time. I have worked on project where there were only two developers, and we still had problems coordinating who was changing which files. A revision control system will allow you focus on the code, instead of worrying about overwriting someone else’s changes.
Hack Attack: How to set up a personal home Subversion server