The World Wide Web Consortium is a beast well too unknown to too many webmasters. Along with maintaining the standards of the web, the w3 lets you validate your web pages and style sheets to find out if the code you used is right.
Who Cares?
If your site works it works right? Unfortunately no. Some browsers overlook css and html problems, while others don’t - which means your awesome website might not look so awesome to some people if the code isn’t squeaky clean. To go even further, Google’s webmaster guidelines makes it pretty clear the things that they look at when deciding what sites are high quality for their search results.
But Don’t Worry
As big a deal as valid code is - you’re not the only one that’s slacking. Most websites on the Internet aren’t valid, and even being mostly valid will put your site above most. Writing HTML is easy - writing a totally valid website is pretty hard (hey - not even Google lives up to their own standards). I did it for us - but I’m not going to lie - that’s a week of my life I want back. So anyway, the next time your website looks awesome in FireFox and your visitors using Internet Explorer v. 0.1.2 beta start complaining - it’s time to validate.