<script type="text/javascript">
  function shoppw(thebox){
    var ps = document.getElementById('ps');
    var pass = document.getElementById('pass');
    ps.removeChild(pass);
    var psImput = document.createElement("INPUT");
    
    if(pass.type == 'password'){
      psImput.type = "text";
    } else {
      psImput.type = 'password';
    }
    psImput.id = 'pass';
    psImput.name = "password";
    psImput.maxlength="15";
    ps.appendChild(psImput);
  }
</script>

<td class="label"> * <label for="password" accesskey="">登录密码：</label></td>
  <td ><div id="ps"><input type="text" name="password" maxlength="15" id="pass" /></div>
   <input name="checkbox2" type="checkbox" value="true" checked="checked" id="show" onclick="shoppw(this)" />
   <label for="show" accesskey="">显示</label></td>