A Google Groups thread asks about hiding content using AJAX and CSS. Google Webmaster Central rep, Wysz, said:
If your text is temporarily "hidden" as part of your site's UI but is still intended for the user to see at some point, you probably don't need to worry about Google mistakenly viewing it as deceptive.
Yes, so my title was a bit deceiving but this question is a common webmaster question.
Many sites deploy styling techniques that only shows content on a specific click. Heck, even Google deploys this on their help content. For example, take a look at this page. Notice that when you click on the links in the middle of the page, you then notice more content appear. Technically, Google is temporarily hiding text from the user until that user clicks on the link.
This is a form of acceptable hidden text, since a user can get to the content while on the same page.
Forum discussion at Google Groups.