One of the reference websites I got a lot of use out of even before I started my current position was W3Schools.
W3Schools is a free site, low noise and high signal. It covers a large swath of technologies, but they are all applicable to someone creating web applications. I had learned HTML from a great reference book from HeadFirst labs, but the tutorials on W3Schools were essential. They are easily referenced from anywhere and help easily demonstrate principles. Most tutorials give you a chance to try code out yourself, without leaving you with a bunch of text files to clean up or installing any tools, perfect for learning on shared machines. I picked up PHP almost exclusively with W3Schools. Even my work with PostGreSQL was greatly simplified by comparing it with the MySQL examples within the PHP examples.
Check out W3Schools if you have to do any web development. It is a great way to get started for a budding web developer.