Surely related to http://issues.ez.no/IssueView.php?Id=15718&activeItem=2, links_and_smileys operator lacks alt attribute when transforming images in cool icons.
That makes w3c validator claim about.

Steps to reproduce

just go to following page and use w3c validator
http://share.ez.carlos/forums/install-configuration/timezone-on-php5-strict-standards-strtotime-solved