What is W3C and what can it do for me?
What is W3C?
The main use of W3c is to help validate HTML and CSS code that is developed across the web to make sure it is properly written and optimized to make the web as efficient a place as possible for browsing and locating information.
Having validated code is also great for SEO to ensure the search engines can properly read your site to index it.
You can at any time check the validity of any page by visiting http://validator.w3.org and entering the URL you wish to test.