学步园

<META http-equiv=Content-Type content="text/html; charset=gb2312">
<style>
.a{border: 1px #E7EFF7 solid;}
.b{border: 1px red solid;}
</style>
<script>
var clickId;
function ChangClass(id)
{
 if(document.getElementById(clickId) != null )
  document.getElementById(clickId).className = "a";
 document.getElementById(id).className = "b";
 clickId = id;
}
</script>
<form id="form1" name="form1" method="post" action="">
  <label>
  <input type="text" name="textfield" class="a" id="I1"/ onclick="ChangClass(this.id);">
  </label>
  1
  <p>
   <input type="text" name="textfield" class="a" id="I2" onclick="ChangClass(this.id);"/>
  2</p>
  <p>
    <input type="text" name="textfield" class="a" id="I3" onclick="ChangClass(this.id);"/>
  3</p>
  <p>
    <input type="text" name="textfield" class="a" id="I4" onclick="ChangClass(this.id);"/>
    4
</p>
</form>