When I read your question I started wondering about my own sites. Here is a link that explains it a little.
http://htmlhelp.com/tools/validator/doctype.html
Since I've been coding html, I've never paid attention to DOCTYPE that is supposed to be the first line in any document. HTML editors add those, but I hand code my pages.
I used http://validator.w3.org/ to validate my main page, and one of the errors is that dtd def is missing. However, the page renders just fine.
So, is dtd even important? Does it affect the speed at which the page loads? Do the search engine robots care?
I tested yahoo and google, none had a doctype. Then cnet.com had a shocking 1370 errors on one page!
Do I need go crazy trying to be standards compliant? Or is it all just hype?

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