Is code validation important in web design?

Something I’ve noticed recently which makes me wonder about people’s understanding of how web design works is the designer/developer obsession with validation. I’m definitely not the first to realise this (i’m pretty sure i read an article not so long ago at jeffcroft.com – where Jeff made the same point), but i’ve been surfing the web a bit this weekend, and noticed how rampant this issue really is. Validation of web sites is a good goal(a best practice), however it is not something that requires you to put a badge on your site.. or a link saying that you are CSS2.1 valid. Customers, clients etc don’t care… they care about whether or not your web site works (preferably in all browsers). Valid code is something all web designers ought to be producing, but you shouldn’t put a badge up on the site.. it’s like putting a badge that says “MY WEB SITE WORKS” – of course it does, the person reading your little badge is viewing the page. This site validated while I was building it, but i think now the CSS is technically invalid (i use the opacity: property a bit). But when a site i build is valid, I’m not screaming it from the rooftops, what if something I add breaks the validation later? Besides.. I take it as a given that a site I produce will validate (at least the XHTML – I sometimes use similar CSS hacks to save time.. shrug). It comes down to a question of pragmatics. In any real world project there comes a time where you have to sacrifice what you KNOW is...