Apple - HTML / CSS / Javascript editor for the iPad?

I think the best one out there is called Textastic. It supports FTP, DropBox and WebDav and has a keyboard geared for editing code. It also has syntax highlighting.

There is also Diet Coda from Panic, designed as a companion for Coda but it can certainly be used independently.

Unfortunately, it lacks support for Dropbox syncing. iCloud syncing exists if you use the App Store version of Coda.

You might also try Kodiak JavaScript: http://www.becomekodiak.com/kodiak-javascript.html. It has syntax highlighting, tabs and keyboard extensions.

Note that I am a co-author of this app, but I hope it is okay to advertise it here, because it seems to be related to the question asked.