document.onkeydown = function (event){
    if (!document.getElementById) return;
    if (window.event) event = window.event;
    if (event.ctrlKey){
        var link = null;
        var href = null;
        switch (event.keyCode ? event.keyCode : event.which ? event.which : null){
            case 0x25:
                link = document.getElementById ('LeftLink');
                break;
            case 0x27:
                link = document.getElementById ('RightLink');
                break;
            case 0x26:
                link = document.getElementById ('UpLink');
                break;
            case 0x28:
                link = document.getElementById ('DownLink');
                break;
        }
        if (link && link.href) document.location = link.href;
        if (href) document.location = href;
    }
}