<p>Form illustrating
   <code>input:focus   </code>
 </p>
 <form method="post" action="http://cscie12.dce.harvard.edu/echo">First name:
   <input type="firstname"/>

   <br/>
Last name:
   <input type="lastname"/>

   <br/>
Email:
   <input type="email"/>

   <br/>

   <input type="submit"/>

 </form>

In style element (<style>) within head element:

input:focus {
  background-color: #ffc;
  border: medium solid orange;
}