This Style Guide helps to sort through a number of formatting-related issues. Developers can refer to it for best practices ideas too. As Google says, "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."
The guide has been made available to developers to be used as per their requirements. Google will provide further insights into the style guide’s design decisions and future updates soon. Meanwhile, do explore the guide and do share your views with us.Google Introduces New Coding guidelines for HTML and CSS!,