For those few that are not familiar with concept of Revision Control I will describe briefly why I choose to use it here, which should also explain the general idea behind the concept.
I will be hacking the template of the blog, this means I will be modifying the "code" of my blog, the reason I want to do this is simple: It affects the way you see it. This "code" is parsed by blogger backend server and rendered into HTML which is later parsed by your browser and displayed to your eyes (which by the way goes another parsing and interpretation by your brain before you can actually "see"/ "read" my blog). Parsing is the process of "understanding" a known format.
Now, due to the known fact that there is no software without bugs. Hacking surly means introducing bugs, considering the fact that I've never edited blogger templates before- The bug factor is even higher. Further more, bugs are here forever or as the saying goes "To err is human, to fix it divine" (A remix of Alexander Pope famous quote "To err is human, to forgive divine" by your humble).
To tackle this bug fixing process in a more profound process, one of the best techniques is going back step by step attempting to isolate what exactly caused the wrong behavior (the bug). This is where revision control system comes in- It allows you to retrieve older versions of the file, further more it allows you to display a difference between 2 versions of the same file in an easily accessible interface. This fits into the previously introduced metaphor of bug tackling: start from something that worked, search revision by revision until you find what broke it, understand why it's broken, fix the problem, ensure the fix works. Some folks forgot the import step of Learn from the error and think how to avoid it next time.
You can open your own Google code repository at the following link Google Code, as for document revisioning, you can do the same thing using Google Docs which allows out of the box "History" of your document modifications.