ERR_TUNNEL_CONNECTION_FAILED: How to Fix It
This one points at a proxy almost every time, often one you did not know was set. Here is where to look and how to clear it in a couple of minutes.
ERR_FILE_NOT_FOUND: What It Means and How to Fix It
This one is about a file on your own computer, not a website. Here is what it usually means, including the extension case that catches most people.
ERR_CACHE_MISS: What It Means and How to Fix It
Usually this is not an error at all, it is Chrome asking whether to resend a form. Here is how to tell the harmless case from the real one.
ERR_NETWORK_CHANGED: What It Means and How to Fix It
Your connection changed halfway through loading, so Chrome gave up. Here is what causes it, including the two settings that make it happen constantly.
431 Request Header Fields Too Large: How to Fix It
A 431 means what you sent before the page was too big, almost always cookies. Here is the two click fix for visitors and the real fix for site owners.
ERR_BAD_SSL_CLIENT_AUTH_CERT: How to Fix It
The site asked your browser for a certificate and did not accept what it got. Here is what that means, and why it is usually a work or bank site.
ERR_CONNECTION_CLOSED: What It Means and How to Fix It
The connection was closed before an answer arrived. Here is how it differs from reset and refused, and seven fixes for visitors and site owners.
ERR_NAME_NOT_RESOLVED: What It Means and How to Fix It
Your computer could not turn the website name into an address. Here is how it differs from NXDOMAIN, and seven fixes starting with the two that usually work.
404 Not Found: What It Means and How to Fix It
A 404 means the address is fine but nothing lives there. Here is what to do as a visitor, and the WordPress fix that takes one click as an owner.
400 Bad Request: What It Means and How to Fix It
A 400 means the server could not understand what you sent. Most of the time it is an oversized cookie. Here is how to check that first, then the rest.