Hola
jjrolevio
Te he retocado un poco el código.
function popUp(URL)
{
day = new Date();
id = day.getTime();
iz = (screen.width-780) / 2;
ar = (screen.height-550) /2;
eval("page" + id + " = window.open(URL, '"+id+"', 'top="+ar+",left="+iz+",toolbar=0,scrollbars=0,loc ation=0,statusbar=0,menubar=0,resizable=0,width=78 0,height=550');");
}
Saludos,