function disableCtrlKeyCombination(e)
    {
        //list all CTRL + key combinations you want to disable
        var forbiddenKeys = new Array('a', 'n', 'c', 'x', 'v', 'j');
        var key;
        var isCtrl;
        if(window.event)
        {
                key = window.event.keyCode;     //IE
                if(window.event.ctrlKey)
                        isCtrl = true;
                else
                        isCtrl = false;
        }
        else
        {
                key = e.which;     //firefox
                if(e.ctrlKey)
                        isCtrl = true;
                else
                        isCtrl = false;
        }
        //if ctrl is pressed check if other key is in forbidenKeys array
        if(isCtrl)
        {
                for(i=0; i<forbiddenkeys .length; i++)
                {
                        //case-insensitive comparation
                        if(forbiddenKeys[i].toLowerCase() == String.fromCharCode(key).toLowerCase())
                        {
                                alert('Key combination CTRL + '
                                        +String.fromCharCode(key)
                                        +' has been disabled.');
                                return false;
                        }
                }
        }
        return true;
    }

    function disableCtrlModifer(evt) {
        var disabled = { a: 0, c: 0, x: 0, v: 0 };
        var ctrlMod = (window.event) ? window.event.ctrlKey : evt.ctrlKey;
        var key = (window.event) ? window.event.keyCode : evt.which;
        key = String.fromCharCode(key).toLowerCase();
        return (ctrlMod && (key in disabled)) ? false : true;
    }