function init_keyboard( left_url, right_url, up_url )
{
    var keyboard = new Keyboard();

    document.onkeydown = keyboard.event;

    this.left_url = left_url;
    this.right_url = right_url;
    this.up_url = up_url;
}

function Keyboard ()
{

    var self = this;

    this.event = function(e)
    {
        if (!e) { e = window.event; }
        // alert(e.keyCode);

        // left arrow
        if (e.keyCode == 37)
        {
//            document.getElementById('prev_button').focus();
            doRedirect(left_url);
        }
        // right arrow
        if (e.keyCode == 39)
        {
//            document.getElementById('next_button').focus();
            doRedirect(right_url);
        }
        // space bar
        if (e.keyCode == 32)
        {
            //document.getElementById('next_button').focus();
            doRedirect(right_url) ;
        }
        // up key
        if (e.keyCode == 38)
        {
            doRedirect(up_url) ;
        }

    }



    function doRedirect ( url )
    {
        if ( url != '' )
        {
            document.location = url;
        }
    }

}