Right Click context menu

On implementing this particular code ,it disables any user input component displayed in the form.Please help me
URL:-http://elouai.com/javascript/javascript-popup-menu.php

<script language="javascript">
<!--
var ie = document.all
var ns6 = document.getElementById&&!document.all

var isMenu = false ;

var menuSelObj = null ;
var overpopupmenu = false;

function mouseSelect(e)
{
var obj = ns6 ? e.target.parentNode : event.srcElement.parentElement;

if( isMenu )
{
if( overpopupmenu == false )
{
isMenu = false ;
overpopupmenu = false;
document.getElementById('menudiv').style.display = "none" ;
return true ;
}
return true ;
}
return false;
}

// POP UP MENU
function ItemSelMenu(e)
{
var obj = ns6 ? e.target.parentNode : event.srcElement.parentElement;

menuSelObj = obj ;
if (ns6)
{
document.getElementById('menudiv').style.left = e.clientX+document.body.scrollLeft;
document.getElementById('menudiv').style.top = e.clientY+document.body.scrollTop;
} else
{
document.getElementById('menudiv').style.pixelLeft = event.clientX+document.body.scrollLeft;
document.getElementById('menudiv').style.pixelTop = event.clientY+document.body.scrollTop;
}
document.getElementById('menudiv').style.display = "";
document.getElementById('item1').style.backgroundColor='#FFFFFF';
document.getElementById('item2').style.backgroundColor='#FFFFFF';
document.getElementById('item3').style.backgroundColor='#FFFFFF';
document.getElementById('item4').style.backgroundColor='#FFFFFF';
isMenu = true;
return false ;
}

document.onmousedown = mouseSelect;
document.oncontextmenu = ItemSelMenu;
//-->
</script>
<!---------------------POPUP MENU-------------------------->
<div id="menudiv" style="position:absolute;display:none;top:0px;left:0px;z-index:10000;" onmouseover="javascript:overpopupmenu=true;" onmouseout="javascript:overpopupmenu=false;">
<table width=82 cellspacing=1 cellpadding=0 bgcolor=lightgray>
<tr><td>
<table width=80 cellspacing=0 cellpadding=0>
<tr>
<td id="item1" bgcolor="#FFFFFF" width="80" height="16" onMouseOver="this.style.backgroundColor='#EFEFEF'" onMouseOut="this.style.backgroundColor='#FFFFFF'"> <a href="#">Item1</a></td>
</tr>
<tr>
<td id="item2" bgcolor="#FFFFFF" width="80" height="16" onMouseOver="this.style.backgroundColor='#EFEFEF'" onMouseOut="this.style.backgroundColor='#FFFFFF'"> <a href="#">Item2</a></td>
</tr>
<tr>
<td id="item3" bgcolor="#FFFFFF" width="80" height="16" onMouseOver="this.style.backgroundColor='#EFEFEF'" onMouseOut="this.style.backgroundColor='#FFFFFF'"> <a href="#">Item3</a></td>
</tr>
<tr>
<td id="item4" bgcolor="#ffffff" width="80" height="16" onMouseOver="this.style.backgroundColor='#EFEFEF'" onMouseOut="this.style.backgroundColor='#FFFFFF'"> <a href="#">Item4</a></td>
</tr>
</table>
</td></tr>
</table>
</div>