Thanks for your input, I'm still not getting any response in the online experiment to letter key presses.
I've tried a number of things:
I've added the JAVA key codes to the responses, suggested by Jon Roberts (thanks), so in addition to 'space','r','g','b' I also have 'Space', 'KeyR','KeyG','KeyB' in the builder response dialogue box. Yet I don't get any movement from the initial screen - unless I press the cursor keys.
I've also looked at the code for the stroop experiment that Jon posted http://psychopy.org/demos/stroop/4
This WORKS for me, I can even save the demo-stroop version from within psychopy and upload the html to my website and this runs (with left, right, down) as responses. If I append keys: "r","KeyR" to the response dialogue I can't use these keys when running, I can still use left, right, down.
So as Anthony McGuffie says, cursor keys work. But I can't get other keys yet, I am able to work around this.
p.s. By changing the answers in the .csv file to "KeyX" and adding "KeyX" to the index.html file I can get letter keys to work.