pageoneresults - 5:34 pm on Jun 2, 2011 (gmt 0) [edited by: pageoneresults at 5:37 pm (utc) on Jun 2, 2011]
Element g:plusone not allowed as child of element div in this context.
Google +1 in its default form does not validate.
<div class="g-plusone" data-size="standard" data-count="true"></div>
The HTML5 method does but the data-size and data-count don't work last time I checked which was about an hour ago. They default to standard and true no matter what you specify.
[edited by: pageoneresults at 5:37 pm (utc) on Jun 2, 2011]