2 parts to this script
=======================================
part 1 - place in the head
======================================

<script language="JavaScript">
//script by www.a1javascripts.com
<!--
        function openWin( windowURL, windowName, windowFeatures ) { 
                return window.open( windowURL, windowName, windowFeatures ) ; 
        } 
// -->

</script>

================================================================
part 2 - place where you want your link to show

<a href="javascript:void()" 
onMouseOver="JavaScript: newWindow = openWin( 'YOUR-WINDOW.html', 'POPUP', 'width=500,height=300,toolbar=0,location=0,directories=0,status=0,menuBar=0,scrollBars=0,resizable=0,screenX=0,left=0,screenY=0,top=0' ); newWindow.focus()""  onMouseOut="javascript: newWindow.close();" onClick=";return false">YOUR-LINK</a>