Similar to this issue from 3 years ago:
https://wordpress.org/support/topic/google-analytics-for-wordpress-outbound-links-xhtml-not-valid?replies=4
My site is failing W3C validation due to the outbound link tracking. When I disable it, the site validates. It only seems to affect outbound links in my blogroll in the sidebar. No other outbound links are affected.
It lists the error as the target attribute of the links "syntax of attribute value does not conform to declared value." The links show up like this:
<li><a href="http://example.com/" target="" onclick="javascript:_gaq.push(['_trackEvent','outbound-blogroll','http://example.com/']);">Example link</a></li>
The validator fails on target="". I assume this should be '_blank', '_top', or '_self' or the target attribute shouldn't be added at all. When I turn off outbound tracking, these links do not have a target attribute.
I'm not sure if this is the same issue someone saw before, but would you know how to fix it? Thanks!
http://wordpress.org/extend/plugins/google-analytics-for-wordpress/