hi please check the below code i am trying to open tab with name and after that try to close that tab but unable to close or else can anyone tell how we can close opened all tab (url1,url2) from parent tab (url) while close parent tab error in firebug is my_window is undefined

 <form name="submitForm1"   target="my_window"  method="POST" action="http://localhost:8080/ADDMIBREP/">
            <input type="hidden" name="uname" value="uname">
            <a HREF="javascript:document.submitForm1.submit();">ADDMIBREPORT</a>
        </form>
        <a HREF="javascript: closepopup() ">remove</a>
    </body>
    <script> 

        function closepopup()
        {
            alert("hi");

            if(false == my_window.closed)
            {
                my_window.close ();
            }
            else
            {
                alert('Window already closed!');
            }
        } <script>