Validation should not be misunderstood - i.e. it doesn't directly affect how a search engine "decides" to rank your site, necessarily. It's true: some badly-formed html can be found on top-ranking sites.
But, so what? So what if I could do a halfway job? Does that mean I should become lax?
No. If you're going to make a site, make it as highly accessible as possible. This means proper coding.
I regularly run my sites through a few tools, just to catch things that might be wrong. I take a look using YSlow, and sometimes I act on its suggestions. Sometimes not. But I also use the W3C validator, and I almost always go down the list and correct whatever is found.
Another thing to keep in mind - faster-loading pages are better in the eyes of the SEs. And better-formed sites, which are more efficient, can help with this.
But, so what? So what if I could do a halfway job? Does that mean I should become lax?
No. If you're going to make a site, make it as highly accessible as possible. This means proper coding.
I regularly run my sites through a few tools, just to catch things that might be wrong. I take a look using YSlow, and sometimes I act on its suggestions. Sometimes not. But I also use the W3C validator, and I almost always go down the list and correct whatever is found.
Another thing to keep in mind - faster-loading pages are better in the eyes of the SEs. And better-formed sites, which are more efficient, can help with this.