<HTML>

<HEAD>

<script>

  function CheckOther(){

    if (x.value == '4')

      OtherEdit.style.visibility = 'visible'

    else  

      OtherEdit.style.visibility = 'hidden'

  }

</script>

</HEAD>

<BODY>



<P>

<select id="x" onchange="CheckOther()">

  <option value="1">Item 1</option>

  <option value="2">Item 2</option>

  <option value="3">Item 3</option>

  <option value="4">Others</option>

</select>

</P>

<p id="OtherEdit" style="visibility:hidden">

  <input type="text" id="OtherBox">

</p>

</BODY>

</HTML>