You can easily tap a file name to open editing space. If you're editing a remote file you will be asked whether the fill be re-downloaded or not.
If you're editing a local file, iOS will automatically save the file everytime you make a change.
Distraction Free Editing
For better coding experience you can hide the file manager and the top navigation bar and leave only the editor space. Simply tap over the Hide File Manager button and pinch out over the editor area.
Video : Distraction Free Editing
If you use external keyboard, use ⌘(Command) + . to finish editing, and the top toolbar will get back on editor area.
There some keyboard shortcuts which you can use while editing a file. In iPad ,just tap and hold ⌘ (Command), there will appear a popup which contains keyboard shortcuts you can use. For complete list of keyboard shortcuts, you can check in Settings - Editor - Keyboard Shortcuts
If you're working on a dropbox based html file, you probably will find that your html file preview is not properly displayed in the built-in previewer browser.
It's because your css file is served over relative path and dropbox doesn't support it.
But don't worry, there's a workaround for this.
You just need to preview your css file with the built-in browser then copy the url to your html file.
Don't forget to save the html file before previewing it.
Video : How to Make the previewer browser working properly with dropbox connection
Extra Keyboard is a shortkey collection to let you access frequently used brackets / characters during programming quickly. Swipe left or right over the light grey button to show different shortcuts.
You can alse create your own shortkey with cursor position support. Simply tap over the plus (+) sign in the right section of extra key bar.
Koder built-in previewer browser comes with HTML View Source and Firebug functions. You can use it by tapping the '<>' icon at the top navigation bar when previewing html file or opening a web page.