:disabled

The :disabled CSS pseudo-class represents any disabled element. An element is disabled if it can’t be activated (e.g. selected, clicked on or accept text input) or accept focus. The element also has an enabled state, in which it can be activated or accept focus.

<!DOCTYPE html>
<html>
    <head>
        <style>
            input[type = "text"]:disabled {
                background: #ccc;
            }
        </style>
    </head>
    <body>
<form action="#">
  <fieldset>
    <legend>Shipping address</legend>
    <input type="text" name="shipping_firstName" disabled>
    <input type="text" name="shipping_lastName" disabled>
    <input type="text" name="shipping_address1" disabled>
    <input type="text" name="shipping_address2" disabled>
    <input type="text" name="shipping_zipCode" disabled>
    <input type="text" name="shipping_town" disabled>
  </fieldset>
  <fieldset>
    <legend>Billing address</legend>
    <label>
      <input type="checkbox" name="billing_is_shipping" value="true" checked>
      Billing address is the same as shipping address </label>
    <input type="text" name="billing_firstName" disabled>
    <input type="text" name="billing_lastName" disabled>
    <input type="text" name="billing_address1" disabled>
    <input type="text" name="billing_address2" disabled>
    <input type="text" name="billing_zipCode" disabled>
    <input type="text" name="billing_town" disabled>
  </fieldset>
</form>
    </body>
</html>