[Bilderback]

Thank you for the great article. I've lately been wrestling with XHTML 1.0 Strict on a Drupal site of mine.(very fun)
Another big problem I see alot of people do is improperly use the HTML commenting.
<!-- This is a comment -->

But often, you will find ugly variations of commenting in many peoples code.
<!------------ This is NOT a comment ------------>

<!------------------------------------------------
--------------- Even worse, people ---------------
------------------------------------------------->

A single extra hyphen can cause problems especially dealing with other template engines.
<!--- Just one extra hyhen will throw off vaildation --->