var win = null;
function openWindow(wnd, _width, _height){
        posx = (screen.width) ? (screen.width-_width)/2 : 0;
        posy = (screen.height) ? (screen.height-_height)/2 : 0;
        settings = 'height='+_height+',width='+_width+',top='+posy+',left='+posx+',scrollbars=no'
        win = window.open(wnd,'popwindow',settings)
        if(win.window.focus){win.window.focus();}
}