I am using show my payment history window as follows..
Code:
<form name="myform" method="post" action="payhistory.php"> <input name="pay_his" type="submit" class="memberhistory" value="Payment history" onclick="myform.target='POPUPW'; POPUPW = window.open('about:blank','POPUPW','width=550,height=400','scrollbars = yes','title= ' );"