body {
    display:flex;
    align-items:center;
    justify-content:center;
}
.form-main {
    display: flex;
    align-items: center;
    justify-content: center;
    width:100%;
}
.form-horizontal{
    max-width:600px;
    background-color:#f3f1f1;
    padding:40px;
    border-radius:10px;
}