When using contentEditable in Firefox, is there a way to prevent the user from inserting paragraph or line breaks by pressing enter or shift+enter?
You can attach an event handler to the keydown or keypress event for the contentEditable field and cancel the event if the keycode identifies itself as enter (or shift+enter).
This will disable enter/shift+enter completely when focus is in the contentEditable field.
If using jQuery, something like:
$("#idContentEditable").keypress(function(e){ return e.which != 13; });
...which will return false and cancel the keypress event on enter.