In professional web development, especially when working in teams of any size, configuration management is one of the most important tasks when it comes to keeping track of configuration changes.
The Wikipedia article for Software Configuration Management states that "In software engineering, software configuration management (SCM) is the task of tracking and controlling changes in the software, which is part of the larger cross-discipline field of configuration management. SCM practices include revision control and the establishment of baselines. If something goes wrong, SCM can determine what was changed and who changed it. If a configuration is working well, SCM can determine how to replicate it across many hosts."