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Shortcut keys code is not working for W,T,N,K and F
Here is the code of three shortcut keys:
$.ctrl = function (key, callback, args) {
    $(document).keydown(function (e) {           
        if (!args) args = []; // IE barks when args is null
        if (e.keyCode == key.charCodeAt(0) && e.ctrlKey && window.event.shiftKey) {
            e.preventDefault();
            callback.apply(this, args);
            return false;
        }
    });
};

$.ctrl('W', function () {
    autoText("[[Windows and cills]]");
});

It will call autoText():
function autoText(value) {
    var txt = value;
    var t = txt.fontcolor("blue");
    var fetch_txt = "  " + t + "  ";
    alert(fetch_txt);
    var span = document.createElement("label");
    span.className = "disabled";
    span.innerHTML = fetch_txt;
    var txtbox_txt = document.getElementById('textbox').innerHTML;
    var newtxt = txtbox_txt;
    document.getElementById('textbox').innerHTML = newtxt;
    document.getElementById('textbox').focus();
    document.getElementById('textbox').appendChild(span);
}

It works for other keys but not W, T, F and N. It is for div tag which is set contenteditable=true id=textbox.
How can I prevent bydefault events?

For security reasons, you can't override those shortcuts. It is generally advised to use Alt for user-defined shortcuts, but even then some can't be overridden for some reason. In the end I used Ctrl+Alt+something for my shortcuts... messy, but it worked without fail.

@NiettheDarkAbsol alt is worked except K and L..

It might be worth trying having some buttons, even if they're hidden offscreen, with accesskey="x", but this would make it different based on the browser and OS. It'd be reliable, since it would always be that button being clicked, but to instruct your users... hmm...
