IE6 (ah bless) is oddly paranoid when rendering https sites. This can be seen when it attempts to use a page that contains a Silverlight application. The problem stems from the default template Visual Studio generates for hosting the application. It contains a invisible iFrame element, apparently to support Safari. However, if you attempt follow the links to explain why Safari needs such a hack you hit a dead-end. Assuming that was because Safari 4 has since been released I tested the previous problem, that you can’t correctly browser-back to a page with SL content. It seems to work fine. However, Ken Tucker pointed out that Silverlight Navigation now requires the use of this iFrame. So the simplest solutions is to add a src="#’ attribute to the iFrame – this doesn’t seem to cause any problems to "modern" browsers and IE6 now understands that the src is secure.