under IE6 with SP1 bad entities are no more allowed in the URI see http://validator.w3.org/docs/errors.html it happens a lot in PLone but Zope is not exempt http://www.zope.org/feedback_site_form?whats_up=Register&origin_url=http://w ww.zope.org/Register will work but it is mere luck, it is not W3C compliant it should be for example instead of &origin &origin Hotmail, Msn, passport.com, passport.net. and my self on my tiny Plone of newbie are not so lucky I am newbie in everything you write about, but I am a very old oldie in matter of html W3C compliant I was in my past teacher, I know it can be difficult to receive such a remark particularly from a not so bright pupil.. but If I dare to write this message it is because I am persuaded it can be important Think to all the bad entities there are every where cgi, asp, php,.. look at in the IE6 list.. there are complaints everywhere but you can't say for once that is really a window bug Have a look on Zope under Amaya from the W3Consortium..