* {
   margin: 0;
   padding: 0;
   font-family: sans-serif;
   box-sizing: border-box;
  }

body
{
     background-image: url("../Imagenes/fondoLogin.jpg");
     background-repeat:no-repeat;
     -webkit-background-size:cover;
     -moz-background-size:cover;
     -o-background-size:cover;
     background-size:cover;
     background-position:center;
}

form {
      margin: auto;
      width: 50%;
      max-width: 400px;
      opacity: 0.9;
      background: hsla(208, 100%, 25%, 0.3);
      padding: 30px;
      border: 1px solid rgba(0,0,0,0.2);
      border-radius: 15px;
     }

h2   {
      text-align: center;
      margin-bottom: 20px;
      color: rgba(0,0,0,0.8);
     }

input {
       display: block;
       padding: 10px;
       width: 100%;
       margin: 30px 0;
       font-size: 20px;
      }

input[type="submit"]:active {
  transform: scale(0.95);
}

@media (max-width: 768px){
  form {
    width: 75%;
  }
}

 @media (max-width: 480px){
  form {
    width: 95%;
  }
}

.error
{
    text-align: center;
    display: none;
}