.header_userguide
{
    text-align: center;
}
.button_userguide
    {
        text-align: left;
        position: absolute;
    }
@media screen and (max-width:992px) {
    .button_userguide
    {
        display:none;
    }
}
.youtube{
    position:relative;
    padding-bottom:56.25%;
    height: 0;
    overflow: hidden;
}
.youtube iframe {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
}