Second I wouldn’t go so far as to completely vilify validation. While I agree that validation isn’t something worth wagging fingers over, it is extremely useful in a production environment.

As you’ve beautifully illustrated, it doesn’t make a spit of difference to today’s user agents which are still accustomed to bruised mark-up but validation is an essential first step in troubleshooting rendering or display issues. Once all the simple, obvious things are accounted for (encoding the required entities, closing open tags, correcting tag case) it’s far easier (and less time consuming) to track down the source of the problem. Otherwise, I need to sort through line after line of the validator harping on inconsequential errors in order to find the real cause—assuming it’s even a problem with the X/HTML! But once the source is valid then I know it’s either a problem with the CSS or a particular browsers misrendering of the CSS.

Being able to eliminate some guess work on the way to a solution and the resulting time savings is reason enough to write valid code.

I validate pages to look for errors in code. If I find no errors, then I know it is a CSS problem. If the CSS validates, I know it is a browser problem and I can begin to work around it.

Validation matters in a production environment, but sites are not always going to be valid. Why? Say you design a site and hand it off to a client. There is no telling what they will do the site once they get a hold of it.

Honestly though, I find a lot more of my display errors during design phase are related to browser quirks than invalid code. What I really need is Doug Bowman or Dave Shea built right into my OS. Kind of like Clippy the Microsoft Office assistant, but with useful stuff to say.

One feature I wish the W3C validator had was the ability to ignore certain errors. For instance, we still have hundreds of unencoded ampersands littering ESPN because of our ad server, and any attempt at debugging based on the validator’s output is tough.

Anybody know of any client-side validators out there which let you turn off certain errors?