Why is Google publisher HTML tag invalid according to W3C specification? Is there any way to correct this example:
<a href="http://plus.google.com/109469573972649651137?prsrc=3" rel="publisher" class="c3">
im not quite sure with your question wether you mean that the google rel=publisher dosnt work for your site, or that it works but w3 is saying its invalid..
if its not working with google you can use the rich snippets testing tool here : http://www.google.com/webmasters/tools/richsnippets
if its working with google but w3 is showing it as invalid, i wouldn't say thats that much of a problem as the code is only going to be used by google so as long as they can read it.. also i think its important to note that search engines, are very good at interpreting html even bad / invalid html so it not being 100% valid isnt something id be too concerned about especially if its just this one link.
i got a hack around it its simple just as in verification of author here if an example