Our HTML and CSS Style Guide, just like other Google style guides, deals with a lot of formatting-related matters. It also hints at best practices so to encourage developers to go beyond indentation. Many style guide authors know the underlying motivation from the question whether to describe the code they write—or to prescribe what code they want to write. Not surprisingly then, in our HTML and CSS style guide you’ll find both (as much as you’ll still find a lot of different development styles in our not entirely small code base).
The post doesn’t go into any detail and even points out that the intent is to simply introduce the style guide and that the folks at Google “hope to share more about its design decisions and future updates with you.”
Not exactly definitive is it? Well, if this is something that will interest you, you may also want to check out the other Google style guides as well. Happy reading!