DNS problems and propagation
Resolution failures, cache behaviour, and why DNS changes take the time they do.
ERR_NAME_NOT_RESOLVED: what it means and 6 ways to fix it
Chrome could not turn the domain name into an IP address. The request never left your machine, which means this is almost always DNS on your side, or a domain that genuinely does not exist.
DNS_PROBE_FINISHED_BAD_CONFIG: what it means and how to fix it
Chrome's DNS lookup failed in a way that points at your resolver configuration rather than the domain. Almost always fixable on your own machine or router in a few minutes.
DNS_PROBE_FINISHED_NXDOMAIN: what it means and 6 ways to fix it
What Chrome's NXDOMAIN error actually says, why it appears for sites that absolutely exist, and the diagnostic checklist that fixes it in under a minute.
ERR_CONNECTION_TIMED_OUT: what it means and how to fix it
Why Chrome's connection-timeout error is usually a local problem, how to tell when it's the site instead, and the ordered checklist that fixes it fast.
DNS propagation: why it really takes hours (and when it doesn't)
DNS doesn't actually propagate, resolvers cache records until their TTL expires. Here's what controls the real wait time and how to speed it up.
Flush DNS cache: exact commands for Windows, macOS, Linux, and Chrome
The right command for every OS, when to use it, and how to verify the cache actually cleared. Plus what flushing won't fix.