[Zope] newbie:cookie expiry problem

This may be very silly plz help I gave this cookie expiry statement in a python script: RESPONSE.expireCookie('login') return context.REQUEST.RESPONSE.redirect('index_html') but when i checked the cookie values in request page, it wasn't removed. the last redirect still worked. when i put an if like this : if (RESPONSE.expireCookie('login')) return context.REQUEST.RESPONSE.redirect('index_html') redirect didn't work. where am i wrong? all the files are in same folder -- Share the vision of difference with ME