In at least one browser (Firefox or IE, don't remember which, but I think it was Firefox), sometimes when the Enter key is pressed, a line break occurs rather than a message transmission. Actually this happened frequently.
I fixed this on my end by: Changing the evaluation of event.keyCode from string to int, and evaluating both 10 and 13 and not just 13.
Revision here:
Note that I represent a customer of CuteSoft, I'm not an employee of CuteSoft; use my tweak at your own risk.
Jon