Well the invalid argument is the name that your trying to give it. Now you can adjust this without using top and left, but i do this because when the user clicks on the link the popup window opens in the middle of the screen. If you dont want top and left, just delete them out of the string.
<script type="text/javascript">
var popUpWin = 0;
function popUpWindow(URLStr, width, height) {
if(popUpWin) {
if(!popUpWin.closed) popUpWin.close();
}
// now this is where you can delete this "top and left".
// If you do, delete, "top, left, screenX, screenY".
var left = document.body.clientWidth/2;
var top = document.body.clientHeight/2;
var input1 = document.getElementById("input1").value;
popUpWin = open(URLStr+'?param1='+input1, 'popUpWin', 'toobar=no,location=no,directories=no,status=no,menubar=no,scrollbar=no,resizable=no,copyhistory=no,width='+width+',height='+height+',left='+left+',top='+top+',screenX='+left+',screenY='+top+'');
}
</script>
<a onclick="popUpWindow('showduty.php',200,200)">click to open</a>
Hope this helps