W3schools.com is the most popular website and very useful for begginer level student or techies.
I already learned lots of language from this website like I have learned first HTML, CSS, XHTML, JAVASCRIPT, SQL, MYSQL, HTML5, PHP and many more.
This website is providing best tutorial and live example. W3schools is created for Learning, Testing and for training program. This website is also provide certification program.
You can test yourself for using this certification program. I’m a web developer so any help needed then I often visite w3school and it will help to fix my query and found some useful information in my work.