I'm running out of things to say. This page is all about a 304 redirect, which again isn't seen all that often in the wild on the server side. At least, I don't think it is. The 304propellertest means "Not Modified", so it's the sort of thing that's particularly useful if you've got a cached version of something that you want search engines to be using instead of whatever it's attempting to request.
I'm really, really running out of things to say - but I need all of these tests to have a decent amount of copy in order to fill the page and give search engines something to read, and to differentiate each of the tests from each other. This is the test that's entirely around 304 redirects, and it's one of the ones that I'm particularly interested in. Here's a little bit more text for you to read, if you want to or have some time to kill.