Package: www.debian.org The http://www.debian.org/distrib/packages.en.html page says this about testing:
This area contains packages that are intended to become part of the next stable distribution. There are strict criteria a package in unstable (see below) must obey before it can be added to testing. See the testing distribution pages for more information. Given that many people interpret this as meaning "a stable version of unstable" I think it would be good to add some words about the security risk involved when running testing. Perhaps something like this: Testing does not get security updates in a timely manner. It is not a good idea to use testing if security is an issue (e.g., if the machine is connected to the Internet). It was a bit of a surprise to me when the security issue was pointed out, even though I should've known better. I have the impression that this is a common mistake, so it makes sense to point it out more prominently. (Descriptions of testing may occur on other places as well, but I was too lazy to search, since I assume the web page developers can easily do a recursive grep.)