$(window).load(function(){

    var alto = $(window).height();
    var ancho = $(window).width();

    if($('#container') != null)
    {
        xPos = (ancho/2) - ($('#container').width() / 2);
        yPos = (alto/2) - ($('#container').height() / 2);
        if(yPos < 0){ yPos = 2; }
        $('#container').css('margin-left',xPos+'px');
        $('#container').css('margin-top',yPos+'px');
    }

});

$(window).resize(function(){
    var alto = $(window).height();
    var ancho = $(window).width();

    if($('#container') != null)
    {
        xPos = (ancho/2) - ($('#container').width() / 2);
        yPos = (alto/2) - ($('#container').height() / 2);
        if(yPos < 0){ yPos = 0; }
        $('#container').css('margin-left',xPos+'px');
        $('#container').css('margin-top',yPos+'px');
    }
});