body {
    display: block;
    overflow: hidden;
    background: url(../IMG/FONDO/Login.gif) no-repeat center center fixed;
    -webkit-background-size: cover;
    -moz-background-size: cover;
    -o-background-size: cover;
    background-size: cover;
    

}
.form-signin {
    max-width: 430px;
    padding: 15px;
    margin: 0 auto;
    color: #FFF; 
}

.cajas.transparentes {
   background-color:transparent !important;
       border:none !important;
}

@media (max-width: 480px){
     #LoginUsuario {
        width: 60%;
        border-radius:60%
    }
}