It is a popular web site for learning web technologies online.it is useful for every type of users whether it is beginner or expert.
That much of infomations it contains.
W3schools contains references and tutorials relating to
PHP
.NET
JAVA SCRIPT
JQUERY
HTML
CSS
JSON
ANGULAR JS
BOOTSTRAP
It has more than one million visitors monthly .
It is founded in 1998 and owned by refsnes data.
W3Schools presents thousands of code examples. By using an online editor, readers can edit examples and execute the code in a sand box.
It has very good UI and it very interactive.
For beginner I strongly recommend this site for learning web tools.
Now we can get the android app of w3 school on play store.