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The user has five minutes to authenticate successfully from the login page (a timer on the page serves as a reminder of the time remaining). If the user attempts to authenticate after this time limit has been exceeded, the following error page is displayed: 
Touchstone requires that the user accepts cookies from the participating web sites, including the login server, idp.mit.edu. If the user disallows cookies, the following error will be displayed when authentication is attempted (unless the application web server detects the problem before authentication): 
Once the user is redirected back to the original web server, the Shibboleth software on that server normally creates an internal session for the user (so that further interaction with the login server for the user is unnecessary). If this session creation fails for any reason, for example if the Shibboleth daemon is not running on the web server, the user will see an error page similar to the following; note that each web application server will likely have a customized version of this page, to match the rest of the site, but, if it has not been customized, the following stock page is displayed:
It is possible for the user to encounter the following error page. This should be very rare. I obtained this screen shot by using the Firefox extension "Tamper Data" and modifying the contents of the data being sent back to the login server when logging in using my username and password. 