What HTTP codes will cause a URL transaction check to report as CRITICAL?

The official policy for HTTP is:

2** - Success
3** - Redirection
4** - Client Error
5** - Server Error

Accordingly, response codes in the range from 300 to 399 are treated by following the ('GET') redirect to an eventual non-3** response. The eventual response is then evaluated based on the following two rules:

1. Response codes in the ...