Earlier quoted context omitted.
The number of webpages with HTML that's just plain wrong (and renders fine!) is staggering. I often wonder what the web would be like if web browsers threw an error upon encountering a syntax error rather than making a best effort to render. If you're writing HTML, you should be validating it: http://validator.w3.org/
Google.com has 39 errors and 2 warnings. Among other things, they don't close their body or html tags. Is there any real downside to having syntax errors?
There is no reason to allow most of these errors other than coding sloppiness.
http://validator.w3.org/check?uri=http%3A%2F%2Fwww.google.co...