Google and Blogger do not seem very inclined in following web standards. The official Google blogs have hundreds of validation errors (see snapshot below) which is because the Blogger template produces invalid XHTML (also read this discussion on the Blogger help group dated 2006).
Those of us who are still with Blogger or plan to shift to Blogger(or Blogspot) will find the following snapshots enlightening and amusing. The first snapshot is of the Official Google blog (439 errors, 171 warnings) and the second one is of the Gmail blog (464 errors, 214 warnings) analyses from the World Wide Web Consortium (W3C) Markup Validation Service. Read the help page on the said site if you are wondering about markup validation and would like to know more. All snapshots are dated 12 February 2010.
Let’s try WordPress.com now (with the default doctype). See the result below (though with XHTML 1.0 strict doctype it gave 14 errors and 1 warning).
Thanks to Richard for the hat tip.