So, we want to write some web application code, do we?
Well, that will require an editor, won't it?
To really dive into web development proper, though, a web-enabled editor is a must.
Brackets is a modern, open source text editor that understands web design.
One interesting feature it provides is the live preview implementing a real-time connection to your browser. Make changes to CSS and HTML and you'll instantly see those changes on screen, providing the power of a code editor with the convenience of in-browser developer tools.
I just now installed Brackets release 1.2 build 1.2.0-15697 from Feb 22 2015.
Here is a two-minute video demonstrating a sample run editing a minimal super simple HTML file, using live preview on it, modifying the HTML and adding a CSS style:
Actually, the YouTube version of this video didn't turn out that nice, so here is a link to the original MP4 recording brackets.mp4 as well.
This is just the beginning... Brackets supports node.js.
There is a whole bunch of other brackets editor YouTube demos to explore in more depth.