General HTML/CSS reference:
My favorite editor:
CodePen is a playground for the front end web.
Show off your latest creation and get feedback. Build a test case for that pesky bug. Find example design patterns and inspiration for your projects.
To cheat on some CSS:
Lightbox is a simple, unobtrusive script used to overlay images on top of the current page. It’s a snap to setup and works on all modern browsers: