What if you want to do one thing if the condition is true, and a different thing if the condition is false? In other words, what if we want to show either one thing or the other, but nobody will see both? The <c:if> on the previous page worked fine because the logic was: everybody sees the first part, and then if the test condition is true, show a little extra.

But now imagine this scenario: you have a car sales web site, and you want to customize the headline that shows up on each page, based on a user attribute set up earlier in the session. Most of the page is the same regardless of the user, but each user sees a customized headline—one that best fits the user’s personal motivation for buying. (We are, after all, trying to sell him a car and become obscenely wealthy.) At the beginning of the session, a form asks the user to choose what’s most important...