Exemple de code du sélecteur CSS :enabled.

<style>
.border{ border:1px solid red }
.cacher{ display:none }
.hidden{ visibility:hidden }

form *:enabled{ border:1px solid green; visibility:visible }
form .hidden *:enabled{ display:inline-block }
</style>
<form>
<span class="border">Du texte</span><br>
<a href="?" class="border">Du texte</a><br>
  <fieldset disabled="disabled" >
    <legend>fieldset</legend>
    <input type="text" class="border" value="Champ non actif">
    <br>
    <input type="text" class="border" value="Champ non actif" >
  </fieldset>
   <fieldset class="hidden">
    <legend>fieldset hidden</legend>
    <input type="text" class="border" value="Champ non actif">
    <br>
    <input type="text" class="cacher border" value="display:none" >
  </fieldset>
  <fieldset>
    <legend>input type="text"</legend>
    <input disabled="disabled"  type="text" class="border" value="Champ non actif">
    <br>
    <input type="text" class="border"  value="Champ actif" >
  </fieldset>
  <fieldset>
    <legend>Display</legend>
    <textarea disabled="disabled" class="border" >non actif</textarea>
    <br>
    <textarea class="border">actif</textarea>
  </fieldset>
  <fieldset>
    <legend>select</legend>
    <select disabled="disabled" class="border">
      <option>non actif</option>
      <option>-</option>
    </select>
    <br>
    <select class="border">
      <option>actif</option>
      <option>-</option>
    </select>
  </fieldset>
  <fieldset>
    <legend>button</legend>
    <button  disabled="disabled" class="border">non actif</button>
    <br>
    <button class="border">actif</button>
  </fieldset>
</form>