Not one of my sites (duh) -- posted for information and (hopefully) interesting comments.

Various people have, over the last few years, done studies into the popularity of authoring techniques. For example, looking at what HTML ids and classes are most common, and at how many sites validate (and yes, we know that we're not leading the way in terms of validation).

http://code.google.com/webstats/index.html

BTW, make sure you notice the section describing Metadata statistics and uses, very enlightening.