W3Schools

1. W3Schools is a web developer information website, with tutorials and references relating to web development topics such as HTML, CSS, JavaScript, PHP, SQL, and JQuery.
2. The site provides a reference manual covering many aspects of web programming, including technologies such as HTML, XHTML, CSS, XML, JavaScript, PHP, ASP, SQL etc.
3. W3schools presents thousands of code examples. By using the online editor provided, readers can edit the examples and execute the code experimentally.

You can  use the website  http://www.w3schools.com/

Also you can use the offline version which is given in below link

Download w3schools(1.66 MB)
Note: This is a compressed file.extract it.

If you find any error in download link,please mention  in comment i will update the link soon