body {
    background: url('../bg-login-2.jpg') no-repeat center center fixed;
    -webkit-background-size: cover;
    -moz-background-size: cover;
    -o-background-size: cover;
    background-size: cover;
}
#bg_lg {
    margin-top: 5%;
    margin-left: 7rem;
}
@media only screen and (max-width: 500px) {
    #bg_lg {
        margin-top: 15%;
        margin-left: 3rem;
    }
}