A few years ago it has become good practice not to design HTML-pages to be beautiful but also to be accessible and well-coded. This lead to a trend that every ( even the not-so-well-formed ) pages usually link to W3-validator ( just like at the bottom right of this blog ). Usually this is a good thing, especially if it proves that the page linking is valid (X)HTML. I'm actually unable to see any deeper meaning in having this link but the subtle message that is "hey, i'm a great coder!". It doesn't make a good page better nor a bad page worse.
But fun starts, at least for me, when a page links to the validator that won't validate. That is, of course, the case for much pages. Negative examples of pages linking can be found everywhere ( www.youtek.it e.g. ). Stop it! It's just embarrassing. Really.