body {
}

#backtt {
    z-index: 20000;
    position: fixed;
    visibility: visible;
    display: block;
    left: 50%;
    width: 450px;
    margin-left: -250px;
    background-color: white;
    margin-top: 166px;
    height: 300px;
    border: 9px solid #808080;
    border-radius: 8px;
}

@media (max-width:767px) {

    #backtt {
        z-index: 20000;
        position: fixed;
        visibility: visible;
        display: block;
        left: 50%;
        width: 395px;
        margin-left: -223px;
        background-color: white;
        margin-top: 166px;
        height: 300px;
        border: 9px solid #808080;
        border-radius: 8px;
    }
}


@media (max-width:767px) {

    #ctl00_imgpopup {
        height: 300px;
        margin-left: 46px;
    }
}