codecademy sign up and locate the app building section very helpful! and other tutorials are there like ja<x>vasc<x>ript, html css, python .....
learn HTML5 & ja<x>vasc<x>ript - fundamentals<br />
HTML5 - http://www.w3schools.com/html/html5_intro.asp <br />
ja<x>vasc<x>ript - http://www.w3schools.com/js/default.asp<br />
For Mobile App Development<br />
if possible also check www.phonegap.com
look around the internet check out you tube and ther websites see if you find some useful info but at the end of the day it all comes down to programing