.signin-form {
    text-align: center;
}

.signin-form [input] {
    width: 100% !important;
}

.centered {
    text-align: center;
}

.center-container-300 {
    position: absolute;
    left: 50%;
    top: 50%;
    width: 600px; 
    height: 300px; 
    margin: -150px 0 0 -300px; 
    border: 1px solid lightgray; 
    border-radius: 10px; 
    padding: 30px;
}

.center-container-400 {
    position: absolute;
    left: 50%;
    top: 50%;
    width: 600px; 
    height: 400px; 
    margin: -200px 0 0 -300px; 
    border: 1px solid lightgray; 
    border-radius: 10px; 
    padding: 30px;
}

.center-container-500 {
    position: absolute;
    left: 50%;
    top: 50%;
    width: 600px; 
    height: 500px; 
    margin: -250px 0 0 -300px; 
    border: 1px solid lightgray; 
    border-radius: 10px; 
    padding: 30px;
}