var win = null;
function NuevaVentana(url,nombre,w,h,scroll){
LeftPosition = (screen.width) ? (screen.width-w)/2 : 0;
TopPosition = (screen.height) ? (screen.height-h)/2 : 0;
parametros =
'height='+h+',width='+w+',top='+TopPosition+',left='+LeftPosition+',scrollbars='+scroll+', statusbar=no, resizable=no'
win = window.open(url,nombre,parametros)
}