// Abre ventana centrada
function ventana(url,nombre,theWidth,theHeight)
{
var theTop=(screen.height/2)-(theHeight/2);
var theLeft=(screen.width/2)-(theWidth/2);
var features="top=" + theTop + ",left=" + theLeft + ",width=" + theWidth + ",height=" + theHeight;
w = window.open(url,nombre,features);
}
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