Q:

Opensource/free HTML5/CSS3/JavaScript IDE?

What is the best open source/free HTML5/CSS3/JavaScript IDE?
Thank you!!!

A:

Most of the time when I write code I am programming C# applications using Visual Studio, which is my favorite IDE. However, when it comes to Javascript VS is quite poor. It does not support collapse to definitions (AKA code folding in other IDEs / editors), does not support code outlining and also has a very primitive and most of the times useless autocomplete.
Because of that, at some point I have started to search alternative tools for JS programming and the best I came across was Aptana Studio. It also has support for HTML and CSS (as well as for some server side languages like Ruby, PHP, Phyton), but I have only used it for JS and that is an area where it shines. It has very good code outlining and one of the best autocomplete implementations I have ever seen for Javascript (even thought it is still improvable).
Aptana Studio is based Eclipse and is available as a plugin or as a full package version. On their site they are saying that the next version is going to totally independent from Eclipse, which would make it a lot more light weight and more performant. However, the current Beta version of Aptana Studio 3 is still based on Eclipse.
You can find more on Aptana Studio 3 on the official page: http://aptana.com/products/studio3

A:

(G)Vim of course. While it might look spartanic at first, it's extremely powerful once you've become familiar with the way it works.

A:

The answers are likely to be subjective, but here are some choices:

KompoZer
Aptana
Amaya

Here are the links: KompoZer, Aptana, Amaya.
This also may help: an extensive comparison of HTML Editors.

