In one of Google’s Matt Cutts recent videos, Matt answered the questions of it is okay to use those expandable web techniques to expand and collapse content. It is okay to use those techniques or is it considered hidden text and against Google’s Webmaster Guidelines.

Matt Cutts said clearly that if it is done for user interests and not to spam or manipulate Google’s search rankings, then it is okay.

Here is the video:

Here is the transcript:

So there you have it, you can hide text only if users can get to it and if it is useful and done not with the intent to trick Google.

Forum discussion at Google+.