As a do-it-yourself webmaster, you probably aren’t going to be starting and/or working on open source projects. But, you might, and more likely, you will be using a lot of open source software. In either case, you will undoubtedly come across something known as a version control system (aka revision control or source control). The two main ones out there are CVS and Subversion (sourceforge has stopped supporting the former in favor of the latter). A version control system basically does what you would guess by its name. But, if you want to know more about the ins and outs of these systems, Kalid Azad offers up a great visual guide to version control on his BetterExplained blog.