There’s no denying creating W3C valid coding for your website can be a pain. Many people dispute its usefulness, claiming that the extra hours spent behind the scenes are not worthwhile since their sites display fine without it.
There are however legitimate reasons and benefits for putting the extra effort into creating W3C valid code which go beyond being able to brag you have a W3C valid site.
Consistency: With the multitude of operating systems, web browsers and versions out there, chances are the majority of your visitors do not share your particular combination. Different browsers do interpret web pages differently, having W3C valid code helps ensure your visitors all see the same thing.
Future-proof content: What’s valid today will be valid tomorrow. While all manner of html hacks and shortcuts can make a website appear fine now, there’s no promise they will work on future browsers. Your best chance for this is W3C valid content.
Web traffic: Admittedly getting solid information out of Google is like trying to draw blood from a stone, but it is widely held that Google gives more traffic to website with valid code than to those without, and while Google doesn’t penalise for not having it, difficulties in reading your site could still lead to a loss in potential traffic. Even without direct confirmation from Google, it surely won’t hurt you to have valid code.
Professionalism: Like anything else in business, is close enough good enough? Your website is an extension of your brand like any other, make it the best it can be.
Competitive edge: If your reading my blog chances are your a designer or a potential client. Even though they may not know exactly what W3C is, many clients demand it.
If a client is tossing up between you and a competitor to design their website, having a valid site while your competitor does not could be the clincher. On the flip side of that, not having it could tilt their decision away from you.
Does your site pass the test?
Personally I think the benefits are worth the effort. If your website doesn’t meet W3C validation standards and you would like it to, two excellent resources are W3Schools and the W3C Markup Validation Service.