<p>Form illustrating
   <code>input:focus   </code>
 </p>
 <form method="post" action="https://cscie12.dce.harvard.edu/echo">
   <label>First name:
     <input type="firstname"/>
   </label>
   <label>Last name:
     <input type="lastname"/>
   </label>
   <label>Email:
     <input type="email"/>
   </label>
   <input type="submit"/>

 </form>

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

input:focus {
  background-color: #FFFFCC;
  border: 2px solid #FF0000;
}
label, input[type=submit] {
  display: block;
  margin-top: 1em;
}