Google Google HTML/CSS style guide suggests omitting head and body tags

All code has to be lowercase: This applies to HTML element names, attributes, attribute values (unless ), CSS selectors, properties, and property values (with the exception of strings). Use valid HTML code unless that is not possible due to otherwise unattainable performance goals regarding file size. Use single ( ) rather than double ( ) quotation marks for attribute selectors and property values.

Source: google.github.io