@media screen and (max-width: 768px) {
     
    body{
        min-height: 100vh;
    }
    main {
        flex-direction: column;
        /*min-height: 100%;*/
        flex: 1 1 auto;
    }
    .vert {
        background-image: url(images/bg-header.jpg);
        opacity: 1;
        height: 250px;
    }
    .head_contact {
    
        color: #fff;
        position: absolute;
        left: 40px;
        bottom: 70px;
        font-size: 1.2em;
        text-shadow: 5px 5px 5px black;
      } 
}