w3c is the standard way of coding web pages. the validation makes sure you are up to date and not using any discontinued ways that might not be correctly.

And it have some value for google rankings too
You can check and find out your problems with w3c in html or css things here: validator.w3.org

W3C = World Wide Web Consortium. It is an organisation that sets the standards for HTML/XHTML, XML and CSS. The organisation's goal is to standardise internet technologies to ensure information on the web can be accessed by anyone on anything i.e. different device platforms.

If you code your web pages to W3C standards in theory they should display correctly in all browsers and on all devices. However, in reality this is not the case because when new standards are set the browser developers take some time to catch up.

Originally Posted by surreypcsupport

W3C = World Wide Web Consortium. It is an organisation that sets the standards for HTML/XHTML, XML and CSS. The organisation's goal is to standardise internet technologies to ensure information on the web can be accessed by anyone on anything i.e. different device platforms.

If you code your web pages to W3C standards in theory they should display correctly in all browsers and on all devices. However, in reality this is not the case because when new standards are set the browser developers take some time to catch up.

I second that. W3C could have been great, if anyone actually bothered to follow its advice. From my own experience, W3C compliance has a very small (if any) effect on SEO, so I honestly don't know if I'd recommend anyone to follow the W3 codec strictly...