Aptana Studio supports syntax highlighting for the array of languages  mentioned above. This helps root out elementary errors such as typos. In addition to syntax highlighting, Aptana Studio supports a code assist feature for HTML, CSS and Javascript. What this does is it visually shows your what elements are compatible with whichever web browsers you are targeting.
 
There is support for internal Javascript debugging with integration to Firefox and Internet Explorer. Not only does Aptana Studio provides debugging for Javascript. It also provides libraries for several Javascript and Ajax Frameworks such as JQuery, Sencha formerly known as Ext JS, Prototype, Scriptaculous and others which help to increase productivity of your projects.