The ErrorSessionTimeout page actually gets called when security is enabled on the portal. My belief is that the location and filename are hardcoded into the portal, becuase there does not appear to be any way to change this page being called. Doing some research I came across the following snippet of code.
Placing the code in the ErrorSessionTimeout.jsp will redirect the user to the defined location. The jsp file is loacted at
Anyway, thinking about it further, there is another options that I completely forgot. Using HTTP Server rewrite rules and redirecting the user to the home page whenever they are directed to the Timout screen.
Living on the Edge
This approach has been solved already and works for a number of things you might want to do with portal. Interesting that one of the things I do with this blog is try and store information that will be useful to different portal teams. I guess it does not help if we forget the things that are discussed?