Straight answers to the things that break quietly: certificates, email deliverability, and why a page will not rank. Each one ends with a free tool to check your own site.
The four things that cause a "Not secure" warning in Chrome, how to tell which one you have, and what to do about each.
What to do when a certificate has expired, why automatic renewal fails silently, and how to stop it happening again.
Why a certificate valid for one address fails on another, how wildcards actually work, and how to check which names yours covers.
The three DNS records that decide whether your mail is trusted, how to tell which one is missing, and what to fix first.
DMARC in plain terms: what alignment means, why p=none protects nobody, and how to move to enforcement without blocking your own mail.
How to tell the difference between not indexed, indexed but not ranking, and actively blocked — and what to do about each.
What Slack, WhatsApp and LinkedIn read when someone pastes your link, why previews get stuck, and how to fix a broken one.
One image size that works everywhere, the minimums each platform enforces, and the mistakes that get an image cropped or dropped.