converse-desktop/resources/css/page-login.css

.login-form {
    color: #777;
    left: 50%;
    position: absolute;
    top: 47%;
    transform: translate(-50%, -50%);
}

.login-form__title {
    font-size: 28px;
    text-align: center;
    font-weight: normal;
    margin: 0px 0px 15px 0px;
}

.login-form__description {
    text-align: center;
}

.login-form__card {
    background: #fff;
    box-shadow: 0px 0px 5px rgba(0, 0, 0, 0.1);
    margin-top: 30px;
    padding: 30px;
}

.login-form__wrapper {
    margin-bottom: 15px;;
}

.login-form__input-group {
    border: 1px solid #ddd;
    border-radius: 0px;
    padding: 0px 0px 0px 30px;
    position: relative;
}

.login-form__input-group:active,
.login-form__input-group:focus,
.login-form__input-group:hover {
    border: 1px solid #aaa;
}

.login-form__input-group .group-prepend {
    position: absolute;
    left: 15px;
    top: 12px;
}

.login-form__input-group .group-append--backgrounded {
    background: #f2f2f2;
    cursor: pointer;
    padding: 12px;
    position: absolute;
    right: 0px;
    top: 0  px;
}

.login-form__input {
    border: 0px;
    color: #222;
    font-size: 18px;
    outline: none;
    padding: 10px;
    width: 290px;
}

.login-form__input::placeholder { /* Most modern browsers support this now. */
    color:  #ccc;
 }

 .login-form__input--with-append {
    width: 260px;
 }

 .login-form__input-help {
    font-size: 13px;
    margin: 4px;
 }

 .login-form__button {
    border: 1px solid #ddd;
    background: rgb(5,93,228);
    background: linear-gradient(0deg, rgba(5,93,228,1) 0%, rgba(76,145,255,1) 100%);
    color: #fff;
    display: inline-block;
    font-size: 18px;
    outline: none;
    padding: 10px 30px;
    width: 100%;
 }

 .login-form__button:disabled {
    background: #eee;
 }

 .login-form__credentials-message {
     font-size: 14px;
    text-align: center;
 }