W3.org teachs you about html,I think its some kind of online class or tutorial but I think you should try to attempt to learn yourself. If you have the time to do it thats what I would do .
Yes, it is a series of tutorials teaching HTML that is hopefully W3 compliant. However to get beyond basic web pages a little more tends to be needed. It's a good start though!
A lot of websites I have built don't pass W3 standards but render just fine in all browsers. I think passing W3 checks is stressed a little too much unless you have a major website then it is a good idea to make sure it certifies.
I think its not that necesarry that you code your site according to W3C standars , unless you are using that site for your own purpose , if yo are going to sell it and your client asks for it then you have to do that , else its not required
w3.org
Linear Mode
