It validates az HTML5 with no </head> and no </body>.

http://ecn.ab.ca/~brewhaha/Moss_Filter.HTM

I actually had to remove the </head> and </body> tags to make it
validate. It looks okay in Firefox 3.5.4 and Explorer eight, so I will
leave it like that for a few days. The attachment, however, *should
cease* to validate.