Newbie question: '3xx result' means?

[green-watch.org]

Greetings irobert,

This should help you out:

http://en.wikipedia.org/wiki/List_of_HTTP_status_codes

The 3xx results on this testing site usually mean found or not modified; there is already a cached version on your computer.

The 4xx results usually mean not found. These usually indicate errors.

This is at least what I interpreted them as. Anybody feel free to correct me if I am mistaken.

Sincerely,
Travis Walters