We currently send some useless junk to the error log. These errors are frequently caused by bots misbehaving or sending bad requests, and are all clearly communicated to the viewer who hits them anyway. They may have served some purpose years ago, but I can't recall them providing any useful information in the last few years.

Bad CSRF tokens:

You are trying to save some data to Phabricator, but the request your browser made included an incorrect token.

Bad "Host" header:

This Phabricator install is configured as "https://admin.phacility.com/", but you are using the domain name "d27urz3c38hyx4.cloudfront.net" to access a page which is trying to set a cookie.

Bad cookie behavior:

Your browser did not submit a "phcid" cookie with client state information in the request.