HTML and CSS - is W3C Validation Realistic?

[jdancing]

I am cranking out specs for a fairly complex web 2.0 style site that will have tons of interactivity, ajax, and various bells and whistles.

I was just going trough my high level requirements and started to wonder if I should put "Site should W3C HTML and CSS validate"

Is a realistic requirement? Is it worth the extra effort and cost if possible? I looked at a ton of popular sites and did found one that validated - craigslist. So I am wondering if a complex site that looks great across browsers and works smooth like 2.0 butter can be made with 100% valid coding or would I need to settle for a craigslist look and feel site?

Since this is a ground up build, now is the time to decide. Thoughts?

[BeeDeeDubbleU]

I suppose it would depend on where your code was invalid.

[pageoneresults]

I suppose it would depend on where your code was invalid.

When performing a validation routine, you can group errors. It's the parsing errors that are the most important. Those are the ones that will cause challenges.

I haven't met a person yet who can tell me exactly what all the parsing errors I've run into over the years may do. I know that mixing XHTML and HTML is not a good practice. In fact, I've read an article where XHTML closing trailing slashes (in the head) caused some problems with indexing on a site that used an HTML 4 DOCTYPE.

[TheMadScientist]

I usually validate when the main template / page is done, then don't worry about it again if I only make minor changes to something... Once in a while I'll go back through and find an error or two and correct those, but for the most part what I do validates when it's originally uploaded, then may have an error or two after editing.

I personally don't think it's important enough to do after every single change to a page or template, but do think it's important enough to do when the main design is done... So I guess my stance is 'get it right' at the time of building and if I add, edit remove (whatever) and the code is 'not quite valid' (maybe I forgot the empty tag on an clear gif: alt="") then it's really not that big of deal to me.

In the situation where I was having someone else build a template I would want it to validate, and if they were in charge of adding the content, then I would want it to validate after they added it, but if I (or someone) changed it a bit and most of the code was unaffected I would probably not worry about revalidating, because I would know it's 'really close to valid' if not 'totally validated', so I'm alright with a small error or two, but validating also helps catch some of the bigger ones that could cause issues, so I usually run through it once when it's originally put online and get it all the way fixed.

There's my .05... No pennies, so you got a bit extra.

[netmeg]

I'm pro validate; not a religious fanatic like pageoneresults, but I aim for it because I'm not the world's greatest coder and I make mistakes and typos, and running things through the validator is the fastest and most efficient way to find mistakes and typos. And because I can be reasonably sure that I'm prepared for any new or unanticipated technology changes.

But I sure wish some of the third party code had the same sensibility. Right now I'm struggling with Facebook Open Graph - you have to do weird things that I don't entirely understand to get it to sort of validate, and I've just about given up. And I'm still hacking away at the standards for mobile. (waves to pageoneresults)

But overall, I definitely think it's a useful exercise. Even if the red stripe throws my OCD into a freak zone.