To make your HTML form responsive for small devices, you can add the following CSS rules to your code:
@media only screen and (max-width: 600px) {
.center {
width: 80%;
height: auto;
}
form .txt_field {
margin: 10px 0;
}
form .txt_field input {
height: 30px;
font-size: 14px;
}
form .txt_field label {
font-size: 14px;
}
input[type="submit"] {
height: 40px;
font-size: 16px;
}
.signup_link {
font-size: 14px;
}
.pass {
font-size: 15px;
}
}