11:14 < Hixie> hsivonen: the most common errors i get are (1) mistyping the 
               start tag (e.g. missing the leading <), and (2) getting hte 
               wrong end tag.
11:15 < Hixie> these two errors both cause an inordinate number of errors to be 
               reported and none of them really say what the actual mistake was.
11:15 < Hixie> e.g. <p> foo var title="">x</vsr> </p>  and  <p> <a 
               href="">x</span> </p>
11:16 < othermaciej> I had a similar experience with the validator
11:16 < othermaciej> although the mistake was missing close "
11:18 < Hixie> the wrong end tag for an inline element in particular cascades 
               into an error for almost every block-level element in the tree 
               from the point of the error on.
11:18 < Hixie> which is exciting when the error is half way down the html5 spec