I was also looking for this too and couldn't find it so I coded it myself.
iPad web based Code Editor (with extra symbols keyboard)
It is a web-based code editor that allows you to type in all the symbols and characters used when programming (brackets, equal sign, tab, quotes...). It is currently in a very early stage so you will need to copy/paste the code, edit, copy/paste again somewhere else (Dropbox, FTP client).
You may also want to check out CodeAnywhere, they have a native app AND also a web-app.