Proper HTML formatting - does it affect SE rating?

[boobookitty]

Originally Posted by Halfdeck

Best practice is to run a site through a validator at least once. No need to fix stuff like &amp; in URLs just make sure you got no major issues (e.g. screwy HTML nesting, unclosed </a>).

I like this one:
http://www.htmlvalidator.com/lite/

I agree that you don't have to be W3 compliant to be spidered. None of my sites are and they get spidered.