502 Bad Gateway: Find Which Server Is Failing and Why
A 502 means one server received a bad answer from another. Work out which layer produced it, then check the app, its process manager, and the proxy settings.
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DMARC Record Not Found: What to Publish and How to Roll It Out Safely
No DMARC record means receivers have no policy for mail that fails authentication. Add a monitoring-only record first, read the reports, then tighten it.
Domain Not Resolving: NXDOMAIN, SERVFAIL and How to Tell Them Apart
A site that will not load may have a DNS problem. Learn what NXDOMAIN, SERVFAIL and timeouts each mean, and trace the failure from the registrar to the record.
HTTPS Not Working: Diagnose It by What You See
Match your symptom (refused, timeout, certificate warning, wrong site) to its cause, then fix it. Includes the exact commands to run from any computer.
Missing HSTS Header: What It Does and How to Add It Without Locking Yourself Out
HSTS tells browsers to use HTTPS only for your site. Learn the safe way to roll it out, with config for nginx, Apache and Cloudflare, and why preload is hard to undo.
Multiple SPF Records: Why It Breaks Email and How to Merge Them
Two SPF records on one domain makes SPF fail with a permanent error. See how it happens, how to spot it in seconds, and how to merge the records safely.
Sitemap Not Found: Why Google Cannot Fetch Yours and What to Check
Search Console says it could not fetch your sitemap. Go through the real causes in order: wrong URL, redirect, robots.txt block, bad content type, or size limits.
SPF Record Missing: How to Find Out and Add One
No SPF record means receiving servers cannot confirm who may send mail for your domain. Check for one with a single command, then build it from your real senders.
SSL Certificate Expired: Check It, Renew It, and Stop It Happening Again
Browsers block sites with an expired certificate. Confirm the expiry date, find out why auto-renewal failed, and fix the part people miss: reloading the server.
Too Many Redirects: Find the Loop with One curl Command
ERR_TOO_MANY_REDIRECTS means two rules send visitors back and forth. Trace the loop, identify the pair (Cloudflare, WordPress, www, proxy) and fix the right one.