Codecademy is a very useful site for technical lover.You can lean many things like HTML, CSS, PYTHON etc.When I am a student lived in a hostel my friend told about this site.Then I search for it and I can learn HTML and CSS in this site.Very useful site the site have online compiler you can check the code that you have wriiten, also they give the very easy steps to make the course very easy.I can learn this two topic near about 1 week.I recommend to all technical lover who is interested about this topic and learn this type of language this site is very useful.