function obrir_finestra1(pagina)
{
var myLeft = (screen.width-370)/2;
var myTop = (screen.height-330)/2;

var opciones="toolbar=no, location=no, directories=no, status=no, menubar=no, scrollbars=1, resizable=no, width=370, height=330, top="+myTop+", left="+myLeft+"";
window.open(pagina,"",opciones);
}

function obrir_finestra2(pagina)
{
var myLeft = (screen.width-370)/2;
var myTop = (screen.height-335)/2;

var opciones="toolbar=no, location=no, directories=no, status=no, menubar=no, scrollbars=1, resizable=no, width=370, height=340, top="+myTop+", left="+myLeft+"";
window.open(pagina,"",opciones);
}

function obrir_finestra3(pagina)
{
var myLeft = (screen.width-370)/2;
var myTop = (screen.height-335)/2;

var opciones="toolbar=no, location=no, directories=no, status=no, menubar=no, scrollbars=1, resizable=no, width=370, height=340, top="+myTop+", left="+myLeft+"";
window.open(pagina,"",opciones);
}
function obrir_finestra4(pagina)
{
var myLeft = (screen.width-350)/2;
var myTop = (screen.height-200)/2;

var opciones="toolbar=no, location=no, directories=no, status=no, menubar=no, scrollbars=no, resizable=no, width=350, height=200, top="+myTop+", left="+myLeft+"";
window.open(pagina,"",opciones);
}