How come IPB validation fails the W3C test and some other big forum softwares pass the test.

Isn't it rather important to pass that test?

test made here

Every single one of those failures came from facebook JS. None were from IPB code.

Also, I just want to point out, nobody really cares about validation.

Your users arent going to go OH MY GOD! THIS SITE IS NOT W3C VALID I AM NOT JOINING!

Ya, you are right :)

I didn

Yeah, disable Facebook Connect and it validates. Facebook doesn't give a rats arse about standards you see.

How come IPB validation fails the W3C test and some other big forum softwares pass the test.

It was once but now there are some few errors

Is'n it rather important to pass that test?

Well it isn't actually if the errors are few, but it show a poor work done by the designer if they are plenty.

Of course google prefer sites that are W3C valid.

A W3C Valid site should (in theory) be look similar with every browser you use, but it is not completely true also if it is a good start point.

More than a W3C Valid site it is important that you check your site with several browsers to see compatibility.

Especially IE7 perform different from FF and also if it is vastly used, many designers don't do IE7 compatible site