Layer pop-up layer jitter problem

layer.open({
        type: 2,
        anim: 5,//Add anim, fade in
        title: 'brand list',
        shadeClose: false,
        maxmin: true, //Open the maximize and minimize buttons
        area: ['800px' , '100%'],
        content: '/Admin/crumbs/brandwindow.aspx' //iframe url
    });