#dotaznicek {
    position: absolute;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    z-index: 10;    
    text-align: center;
    background: url(dark.png);
}

#dotaznicek iframe {
    width: 600px;
    height: 400px;
}

#dotaznicek .dot-content {
    width: 600px;
    padding: 20px;
    background: #FFF;
    margin-left: auto;
    margin-right: auto;
    margin-top: 30px;
    text-align: right;
}