The majority of this chapter is conceptual rather than hands-on, so the opportunities for missteps are fewer than if this were a chapter focused on technical administration. Just remember that anytime you work within the ZMI, you have opportunities to press the wrong button or change the value of a field, giving your entire site pink text, for example. The omnipresent Undo action is there for you if you need to use it.
For modifying base_properties or a custom style sheet, the Undo action will work, but it will roll back the entire file. In other words, if you make 10 changes within base_properties , apply the changes, and then decide that you don't like something, the Undo feature will return you to the previous incarnation of base_properties ”with all 10 modified items reverting to their previous state. Thus, if you are planning to make a lot of stylistic changes, you might want to make your changes incrementally rather than all at once.