Sometimes while browsing through the iTunes Music Store, clicking some link will suddenly bring you to a page saying that the Music Store is "Temporarily Unavailable." It could be a network connection failure, or a DNS failure or something, and it shouldn't be much of a problem, except that the Back button is now disabled. This prevents you from going back and re-trying your last request. This also means that you have lost your entire effort of browsing/searching through iMixes and albums! You now have to go through the whole hunt-n-peck search again to find the album you had finally arrived at. That seems like a design mistake by Apple, as a normal web browser would let you go back to the cached previous page, and iTunes certainly caches the pages it downloads.
But I stumbled on a way to get back to the previous page in this situation. If you hit Command-B, the store will switch to browse mode. If you hit it again, you will be back to the page you were just on. Since I get the "Temporarily Unavailable" page fairly frequently for some reason, I was getting frustrated at it. Hopefully other people running into the same problem will be able to use this hint.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20040512215621513