When I "upgraded" to Mozilla Firefox 40.0, only 1 window in Michael Kraft's Session Manager Add on came up with 40.0. My other 7 Windows that I previously had available in my default session that I used for Mozilla Firefox 39.0.3 simply disappeared. Hence, I had to revert back to using Mozilla Firefox 39.0.3. When I did this, my previous sessions again became available. These same things occurred when I subsequently attempted to "upgrade" to Mozilla Firefox 40.0.2. It is obvious that Michael Kraft's Session Manager 0.8.1.7 does not work with Mozilla Firefox 40.0 and above. However, I began to notice a strange anomaly with this version in Mozilla Firefox 39.0. Prior to Firefox 39.0, my saved default session was between 600K and 700K. Beginning with Firefox 39.0, the size of these same saved sessions suddenly increased to between 3 and 4 Meg. Obviously something had changed, although Michael Kraft's Session Manager 0.8.1.7 still works with Firefox 39.0.3, but not with Firefox 40.0+. I attempted to communicate with Michael Kraft, but was unable to find any email address or other way to contact him. Richard A. Landkamer