.contenedor{
    width: 100%;
    height: 100vh;
    position: relative;
    display: -webkit-box;
    display: -ms-flexbox;
    display: flex;
    -webkit-box-align: center;
    -ms-flex-align: center;
    align-items: center;
    -webkit-box-pack: center;
    -ms-flex-pack: center;
    justify-content: center;
    background: url('../img/back.jpg');
    background-size: cover;
    background-position: top center;
    background-repeat: no-repeat;
}
.cont_logo{
    max-width: 70%;
    width: 100%;
    height: auto;
    display: block;
    position: relative;
}
.logo{
    width: 100%;
    height: auto;
    display: block;
}
.url{
    max-width: 230px;
    width: 100%;
    height: auto;
    display: block;
    margin: 30px auto;
    color: #666;
    text-decoration: none;
    text-align: center;
}