The simplest way to make Google Plus One code to validate:
Just put <div class=”g-plusone”></div> instead of <g:plusone></g:plusone>.
Drawbacks: you cannot add parameters such as ‘count’ or ‘size’, or the code will not be valid any more.
It’s Google’s proposed code for HTML5, but will work for other (X)HTML flavours.
In HTML5 you CAN add parameters such as ‘data-count’, data-size’, etc.
