Why do I have trouble using my browser's "Back" button beyond the CalNet login screen for the proxy server?

Logging in with a CalNet ID and passphrase triggers a series of exchanges among two campus servers and your browser. Unfortunately, if you try to use your browser's "Back" button to go back to a page you visited before logging in, this may cause you to see a message such as this:

Clicking on the "Back" button repeatedly may or may not get you beyond this roadblock, depending on your browser and what pages it has visited. Whatever you do, do not click on the "Reload" button.

If you want to move back to a page you viewed before logging in, a better solution is to use the tool provided in your browser for displaying a pop-up menu of pages you have visited. This can usually be done by clicking on the "Back" button and holding the mouse button down, or clicking on a small down-arrow or "Go" pulldown next to the "Back" button. The browser's "History" function may also be useful.