rocknbil - 3:42 pm on Mar 12, 2012 (gmt 0)

That's exactly (one of the things) XHTML was designed to do. You write a custom DDT to define those "ignore me" tags.

There are so many ways to (accidentally) get content ignored already. One of them is one of the most popular web 2.0 "effects," to put your content behind Javascript using Ajax without alternate content. :-)