If you want to learn to develop, the best site to start is W3Schools.
It's undoubtedly one of the great sites to learn how to program, in the site you can find tutorials for users who are just beginning to learn and even tutorials for advanced users or experts in the subject, the site also has test sections where you can see examples of the subject you are seeing at that time and even practice with the knowledge previously acquired.

Some of the programming languages you can find to learn on this site are: HTML (all versions), CSS (all versions), Javascript, PHP, SQL, JQuery, among many others.

All the website is in English although in spite of this everything is written in a simple and easy way to learn so even users who do not have knowledge about this language could easily understand the examples with the translation provided by Google Translator.

All their courses, examples and tutorials are free and if you need it you can certify with them in any of the languages they offer for a small payment of $95 USD.