Note

Refer to Google HTML/CSS Coding Standard for details.
Use HTML 5: HTML5 (HTML syntax) is preferred for all HTML documents <!DOCTYPE html>. ?

Selected Rules

Omit the protocol from embedded resources: <script src="//www.google.com/js/gweb/analytics/autotrack.js"></script> ?
Use only lowercase for HTML/CSS element names/attributes/values (unless text/CDATA): color: #e5e5e5; ?
Remove trailing white spaces. ?
Do not close void elements, i.e. write <br>, not <br />. ?
Do not omit optional tags. It is optionally suggested to omit optional tags in Google guide; However for compliance considerations we don't implement this rule. ?
Omit type attributes for style sheets and scripts. ?
Use a new line for every block, list, or table element. ?
Use double " rather than single quotation marks ' around attribute values. ?
Abandoned: Indent by 2 spaces at a time. ? -> ?