As I stated before, you must use window.opener to refer to any object in the window that opened the current document. In the example you gave, the reference would be: window.opener.document.parentwinowform.element[0].value. I know this works, because I use it often.
It is also possible to use a relative path to your
jsp. It's the same as any other reference in a web application. The path is relative to the current page, so if the current page is in /myApp/, the reference would simply be "mypage.jsp"