conforms to the W3C standard is the development trend of the website at present, almost all browsers use the W3C standard, W3C standard to ensure your site have obtained consistent performance in all major browsers, you no longer need like that at the end of 90s, to a different browser output different content.
W3C has a number of standards, and there are HTML, XHTML, and CSS for website construction. For these standards, you can refer to the following article or resource:
W3C official website of some information
abroadSome of the domestic
and W3C standards related to