function popup_catalogo(){
var w = 480, h = 340;
if (document.all || document.layers) {
   w = screen.availWidth;
   h = screen.availHeight;
}
var popW = 750, popH = 550;
var leftPos = (w-popW)/2, topPos = (h-popH)/2;

window.open('catalogo.html','catalogo','resizable=0,toolbar=0,location=0,directories=0,status=0,menubar=0,scrollbars=0, width=' + popW + ',height=' + popH + ',top=' + topPos + ',left=' + leftPos);
}

function popup_venta(){
var w = 480, h = 340;
if (document.all || document.layers) {
   w = screen.availWidth;
   h = screen.availHeight;
}
var popW = 750, popH = 550;
var leftPos = (w-popW)/2, topPos = (h-popH)/2;

window.open('venta.html','venta','resizable=0,toolbar=0,location=0,directories=0,status=0,menubar=0,scrollbars=0, width=' + popW + ',height=' + popH + ',top=' + topPos + ',left=' + leftPos);
}

function popup_contacto(){
var w = 480, h = 340;
if (document.all || document.layers) {
   w = screen.availWidth;
   h = screen.availHeight;
}
var popW = 750, popH = 550;
var leftPos = (w-popW)/2, topPos = (h-popH)/2;

window.open('contacto.html','catalogo','resizable=0,toolbar=0,location=0,directories=0,status=0,menubar=0,scrollbars=0, width=' + popW + ',height=' + popH + ',top=' + topPos + ',left=' + leftPos);
}