function return_false(e){
	event.returnValue = false;
}

function prevent(e) {

	var key, type

	key =  event.keyCode;

	type = event.srcElement.type;
	
	if ((type == "input") || (type == "textarea")) return true;

	if (event.ctrlKey == true){

		if((key == 67) || (key == 86)){

			return true;

		} else  {

			event.returnValue = false;
			return false;

		}

    }

	if (event.altKey == true){

		event.returnValue = false;
		return false;

    }

	if (event.shiftKey  == true){


		if (key == 8 && event.type != null) {

			event.returnValue = false;
		    return false;

		}
		return true;

	}

	if (event.type == "click") {
			return true;
	}

	if (event.button == 2 || event.button == 3) {
		event.returnValue = false;
        return false;
    }


	if ((type == null)  && key == 8) return false;

	if (type == null) return false;


		return true;


}

document.oncontextmenu = function(){return false};
document.ondragstart   = prevent;
document.onselectstart = prevent;
document.onDragDrop    = return_false
document.onMouseUp     = return_false
document.onkeypress    = prevent;
document.onkeydown     = prevent;

document.onkeyup       = prevent;
document.onclick       = prevent;
document.onmousedown   = prevent;