Question

I have this jsFiddle: http://jsfiddle.net/RGmNz/6/

And have tried to disable CTRL + B and CTRL + U etc…

  $("iframe").contents().find("body").keydown(function(a,b){

        if(a.which ==32 && a.ctrlKey){
            a.preventDefault(); 
           }
    });
})

But it still bolds the text!

Answer 1

It works if you make two changes: (1) Use the right keycode for b, i.e., 66 rather than 32, and (2) add a call to .stopPropagation():

if (a.which == 66 && a.ctrlKey) {
    a.preventDefault();
    a.stopPropagation();
}

Demo: http://jsfiddle.net/RGmNz/7/

Or you can return false which is the equivalent of both .preventDefault() and .stopPropagation().