.content-wrapper {
    text-align: center;
    background-image: url(../img/bg.jpg);
    background-size: cover;
    background-attachment: fixed;
    background-position: center center;
    background-repeat: no-repeat;
}

img {
   margin: 0 auto;
   margin: 0 auto;
   vertical-align: bottom;
}

@media screen and (max-width: 780px) {
   img {
      width: 100%;
   }
}