:invalid

/* Selects any input element, but only if its current value is invalid */
input:invalid {
  background-color: #ffdddd;
}

:invalid

<form>
  <label for="url_input">Enter a URL:</label>
  <input type="url" id="url_input" />
  <br />
  <br />
  <label for="email_input">Enter an email address:</label>
  <input type="email" id="email_input" required/>
</form>

input:invalid {
  background-color: #ffdddd;
}

form:invalid {
  border: 5px solid #ffdddd;
}

input:valid {
  background-color: #ddffdd;
}

form:valid {
  border: 5px solid #ddffdd;
}
  
input:required {
  border-color: #800000;
  border-width: 3px;
}

input:required:invalid {
  border-color: #C00000;
}

:invalid {
? box-shadow: none;
}

:-moz-submit-invalid {
? box-shadow: none;
}

:-moz-ui-invalid?{
  box-shadow: none;
}