NuestraRED.org/portalcautivo/css/estilos.css

body{
  background: url(captiveportal-imagen_central.jpg);
  background-position: center;
background-repeat: no-repeat;
background-size: cover;
}
  .register {
    background: -webkit-linear-gradient(left, #3931afb5, #00c6ff);
    margin-top: 3%;
    padding: 3%;
  }

  .register-left {
    text-align: center;
    color: #fff;
    margin-top: 4%;
  }

  .register-left input {
    border: none;
    border-radius: 1.5rem;
    padding: 2%;
    width: 60%;
    background: #f8f9fa;
    font-weight: bold;
    color: #383d41;
    margin-top: 30%;
    margin-bottom: 3%;
    cursor: pointer;
  }

  .register-right {
    background: #f8f9fa;
    border-top-left-radius: 20% 50%;
    border-bottom-left-radius: 20% 50%;
  }

  .register-left img {
    margin-top: 15%;
    margin-bottom: 5%;
    width: 25%;
    -webkit-animation: mover 2s infinite alternate;
    animation: mover 1s infinite alternate;
  }

  @-webkit-keyframes mover {
    0% {
      transform: translateY(0);
    }
    100% {
      transform: translateY(-20px);
    }
  }

  @keyframes mover {
    0% {
      transform: translateY(0);
    }
    100% {
      transform: translateY(-20px);
    }
  }

  .register-left p {
    font-weight: lighter;
    padding: 12%;
    margin-top: -9%;
  }

  .register .register-form {
    padding: 10%;
    margin-top: 10%;
  }

  .btnRegister {
    float: right;
    margin-top: 10%;
    border: none;
    border-radius: 1.5rem;
    padding: 2%;
    background: #0062cc;
    color: #fff;
    font-weight: 600;
    width: 50%;
    cursor: pointer;
  }

  .register .nav-tabs {
    margin-top: 3%;
    border: none;
    background: #0062cc;
    border-radius: 1.5rem;
    width: 40%;
    float: right;
  }

  .register .nav-tabs .nav-link {
    padding: 2%;
    height: 34px;
    font-weight: 600;
    color: #fff;
    border-top-right-radius: 1.5rem;
    border-bottom-right-radius: 1.5rem;
  }

  .register .nav-tabs .nav-link:hover {
    border: none;
  }

  .register .nav-tabs .nav-link.active {
    width: 100%;
    color: #0062cc;
    border: 2px solid #0062cc;
    border-top-left-radius: 1.5rem;
    border-bottom-left-radius: 1.5rem;
  }

  .register-heading {
    text-shadow: rgb(0, 0, 0) 0px 2px 3px;
    color: white;
    text-align: center;
    margin-left: 10px;
    margin-top: 10%;
    margin-bottom: -15%;
    border-top-left-radius: 35px;
    background: -webkit-linear-gradient(left, #3931af, #00c6ff) !important;
  }

  .tab-content {
    padding-top: 1em;
  }

.boton_entrar{
margin-left: auto !important;
margin-right: auto !important;
}

  .circle_button {
    box-shadow: 2px 4px 0 2px rgba(0, 0, 0, 0.1);
    border: .5em solid #c7d400;
    font-size: 1em;
    line-height: 1.1em;
    color: #ffffff;
    background-color: #76be4e;
    margin: auto;
    border-radius: 50%;
    height: 7em;
    width: 7em;
    position: relative;
  }

  .circle_button:hover {
    color: #ffffff;
    background-color: #226093;
    text-decoration: none;
    border-color: #c7d400;

  }

  .circle_button:visited {
    color: #ffffff;
    background-color: #c7d400;
    text-decoration: none;

  }

  .circle-link-greater-than {
    font-size: 1em;
  }

@media screen and (max-width:990px) {
.register .nav-tabs {
  width: 90%;
}

}

@media screen and (max-width:768px) {
.register-left  {
  margin-top: 0px;
}
.register-left p {
  font-weight: lighter;
  padding: 0px;
  margin-top: 0px;
}
.register-heading{
  font-size: 21px;
}
}