If it's really poorly coded, that may have an effect, but simply not being "valid" is totally irrelevant.
Google measures the HTML performance to determine where it will rank in its results. Even if it is minute.
A slight invalidity is not a performance issue. The two things are not the same.
I also used to know a small web developer who insisted that every page was HTML valid.
I know someone who insists that the spoon always be behind the teacup, with the head of the spoon to the left. Like civilization itself depends on it or something. Meh. I always put it around the other way just to be spiteful. :lol:
Although many pages from major sites are not HTML valid.
Exactly. Because they know it's irrelevant and they've got better things to do, like rake in megabucks. (Not that those sites are necessarily good, but still ...)
It's certainly a good discipline to check the validity of pages, so I'm not making fun of that, by the way. But it's pointless getting obsessive about it. A valid page is not a badge of honor (though some people like to put silly badges on their sites :rolleyes: ). It's just good to make sure there aren't glaring errors that will break the page.