W3C Validation is important, even though most have never even heard of it. It means your site is coded correctly, with all the right bits in the right places.
Ensuring all of our Websites are validated by W3C means that your website will render correctly in most if not all browsers. It is also the best way to try to ensure the website has the best chances of appearing as high as it possibly can on the search engines.
Why W3C Validation isn’t always possible…
Whilst W3C Validation is evidence of professionalism, most of the time 100% Validation isn’t possible. Some, if not most website design specifications are so specific, and our customers know what they want, that sometimes we have to break the W3C rules slightly to achieve this [us and every other website design company who’s ever written a line of code], this isn’t a bad thing and the websites will still render correctly in all major browsers, so it can sometimes be a play off between the two. We will inform the customer that doing so will effect W3C validation, but if they want a certain layout more; then so be it.
If you visit the W3C validator, and type in any of the most popular websites, eBay (www.ebay.co.uk), Google (www.google.co.uk) and even the W3C Validator itself (https://validator.w3.org) none of them validate. This doesn’t mean they are not professional websites, nor that the their developers do not know what they are doing, it simply means the layout and functionality they desire just doesn’t quite fit with W3C current standards. Some would argue that W3C is way behind in the web development world, but with things changing so fast, and it would be impossible for all options to be covered, so it can be forgiven. As long as the main parts of the website validate and it doesn’t show very obvious errors (as in images with no alt tags, html tags where they really shouldn’t be etc), then I would consider that as a pass as would most others. It is a good tool to ensure obvious errors aren’t made and the basics have been covered.