event.preventDefault()

// defining flags
var isCtrl = false;
var isShift = false;
$(document).ready(function () {
    // action on key up
    $(document).keyup(function (e) {
        if (e.which == 17) {
            isCtrl = false;
        }
        if (e.which == 16) {
            isShift = false;
        }
    });


   $(document).keydown(function (e) {
        if (e.which == 17) {
            isCtrl = true;
        }
        if (e.which == 16) {
            isShift = true;
        }

if ((e.which == 110 || e.which == 78) && isCtrl) {
            e.preventDefault(true);
}
});