w3.org Validation Anyone?

I have never bothered with getting 100% ok.

I only concern myself with what I consider to be serious errors.

I don't think a bot/software could actually fix HTML errors, if they do, it may result to a different look/design than you actually desired.

I fix mine by hand and I get 100% validation on a new blog/sidebars, etc. But the minute you start cut/pasting articles, that tends to go away, unless you are very careful. So I doubt my blogs validate at the moment.

I don't think there are any automatic programs that will really fix your coding - especially on a dynamic site. Tidy does a pretty decent job on a static html page. But (as mentioned above) you may find your site suddenly looking a bit different, since tidy just fixes code - it does nothing for design. And it can sometimes REALLY mess up your page if you are starting with serious errors.

I also code all my sites or vBulletin skins by hand, that way I know they are css/xhtml valid.

This is a really interesting question, and I'm glad you've brought it up.

W3C validation is important, in my eyes. It ensures that your markup ((X)HTML) and CSS is valid, specific to the document type you've specified at the start of your web pages.

Does a non-validated web page make any practical difference to the layout / look of your web page for your visitors?
Probably not. However, the validator is a useful tool to use if your web site isn't displaying properly and you can't figure out why. It can detect missing closing tags, which again, are a small but common issue that sometimes you can't see, because you're so engrossed in the code you're working on.

Is it essential to get 100% validation?
No, but from experience, it's not hard to achieve - and specifications are there for good reason; because the browsers (should) also follow them, which results in web sites that 95% work across most browsers without any tweaks or hacks.

Yes - Internet Explorer "breaks" how our markup works, especially IE6 - but from experience, I've found a validated page will still 90% work in IE6, and with IE7, and IE8 moving towards a better rendering engine that's more consistent, we're starting to converge towards the point where our validated web page should, with a couple of amends, just work.

Bear in mind that most validation errors have a knock on effect for other errors - so fixing one fixes 5, 10, even 20 other validation errors. Some common validation issues are:

• Images - specifying ALT tags
• Links with arguments - using the ampersand instead of &alt;
• Forms - different document types specify different attributes for forms and their field elements - for example, XHTML Strict requires form elements to be nested inside a parent element, such as a paragraph or div - wheras HTML Transistional doesn't require this.

I validate all of my pages/themes/designs...which are hand coded. I KNOW that when I have finished building a wordpress theme, site, etc it validates 100% for it's specific doctype...If whoever I am coding it for makes changes after the fact that breaks validation, I KNOW and have documentation that when I finished the project it was 100% validated and working.

I DO think it's important and I'll tell you why. Even If you don't care about web standards (which many don't) every time a new version/upgrade of a browser is released it has the potential of "breaking" sites that don't validate for their doctype. Spend a few weeks fixing sites that looked fine a week ago, but with your newest IE upgrade look like crap (as IE evolves...we hope) and you will appreciate valid code.

I heard Google has some kind of Webmaster Tools that will help you optimize and improve your site coding to validate it correctly.

A fantastic little software program called Tidy can help you tremendously. Tidy is a free program that you can get at w3.org/People/Raggett/tidy/.
With Tidy, you can clean up your HTML files and remedy syntax problems quickly. Tidy will alert you to non-standard problems in your HTML source and give you warnings as well as error messages. Tidy can also "pretty print" your HTML files, allowing you to line up HTML elements on a page with uniform indentation and margins, so that your HTML file is easier to look at and maintain.

You can get a free HTML editor for Windows 95/98/NT/2000 with integrated support for Tidy at evrsoft.com A text and HTML editor for Windows with built-in support for running HTML Tidy is available at notetab.com These tools help you quickly and easily produce HTML that conforms to standards.

100% compliance isn't too hard to achieve... all my templates validate - well, at least until the client starts adding content

Actually, there are some good content editors available for CMS systems that help the client produce XHTML validating content. bueditor and markitup are much better than tinymce in this respect.

I like to ensure that all my pages validate but mainly from an accessibility and quality point of view. There's still little or no benefit of validated code in terms of SEO.

That's not hard to do if you know what your doing with your XHTML / CSS.
But at the beginning it gets tricky if you are inexperienced coder.