Some sites require you to provide different information on different pages (for example, a username on the first page, and a password on a subsequent page). This will not work with a Simple Form Authentication method, so you will need to use a different method to authenticate to the site here.
Challenge: Some sites use multiple pages to log in, which requires more in-depth use of macros or traffic. Hint: You'll be forced to make a macro or traffic. Simple Form Auth won't work here!