WYSIWYG XHTML case corrector

Drupal 6 outputs XHTML 1.0 strict by default. As of W3C standards, all elements ("tags") as well as their attributes have to be defined lowercase, e.g. <br /> instead of <BR />.

Unfortunately, almost any existing WYSIWYG does not pay respect to this and, instead, sticks to the common Javascript/jQuery habit to regard and output DOM element names uppercase. Thus, almost no page content created in one of these editors will ever display standard compliant code.

This input filter corrects tags on a simple regex base and transforms all element identifiers to lowercase. Just place it into your input formats. Due to the nature of it's task, it is best placed near the end of any filter array.