Guides
How-to and concept guides to get the most from the tools — from root cause to fix.
Why DNS Propagation Is Slow and How to Check It
Why DNS changes aren't instant (TTL, caching) and how to check and speed up propagation.
Fixing SPF 'Too Many DNS Lookups' (permerror)
Diagnose and fix SPF permerror caused by exceeding the 10 DNS-lookup limit via flattening.
SSL Certificate Errors (NET::ERR_CERT…): Causes and Fixes
Five common causes of browser SSL errors and authorized=false, and how to fix each.
Safely Moving DMARC from p=none to quarantine to reject
A safe, staged process to strengthen DMARC from monitoring (none) to quarantine and reject.
Fixing Mixed Content Warnings
Why mixed content warnings appear on HTTPS pages and how to fix active vs passive resources.
Subnetting & CIDR Basics: Splitting a /24
What CIDR notation and subnet masks mean, with a worked example of splitting a /24.
301 vs 302 vs 307/308: Choosing the Right Redirect
The difference between redirect status codes and how to pick the right one for SEO and method preservation.
Core Web Vitals (LCP, CLS, INP) Improvement Checklist
What LCP, CLS and INP measure, and a practical checklist to improve each score.
Why Email Lands in Spam: SPF, DKIM and DMARC Together
Common reasons sent mail goes to spam, and how to align SPF, DKIM and DMARC together.
Essential Security Headers Guide (CSP, HSTS, X-Frame-Options)
The security headers you must set, what each does, recommended values and common mistakes.
Fixing CORS Errors: Access-Control-Allow-Origin Explained
Why the browser throws CORS errors and how to fix each case — preflight, credentials and the wildcard trap.
How to Write robots.txt: Syntax, Examples and Common Mistakes
robots.txt rule syntax, ready-made examples by site type, and the common mistakes that break indexing.
How to Read Email Headers: Trace Senders and Spot Phishing
Open the raw headers, trace the real sending server, and use SPF/DKIM/DMARC results to spot forged mail.
Cron Expressions Explained: Mastering the Five Fields
What each of the five crontab fields means, the patterns you actually use, and the timezone/DST traps.
Checking and Delisting Your Mail Server from DNSBLs
Find out if your sending IP is on a spam blocklist, fix the root cause, and request delisting per list.
Using UTM Parameters Properly: Naming Rules and Pitfalls
How to use utm_source, medium and campaign correctly — naming conventions, GA4 channel mapping and mistakes.
Setting Up hreflang: Stop Multilingual SEO Duplication
Configure hreflang correctly for multilingual sites and avoid the x-default and return-tag mistakes.
HTTP/1.1 vs HTTP/2 vs HTTP/3: Differences and How to Enable Them
Multiplexing, header compression and QUIC — what each version changes, and how to enable and verify it.
WordPress Security Basics: 10 Checks That Stop Most Hacks
The common ways WordPress gets hacked, and the login, plugin, file-permission and header settings that stop them.
DNS Record Types Explained: A, AAAA, CNAME, MX, TXT, NS
What each DNS record type does, real value examples, and rules like CNAME restrictions — beginner-friendly.
Public vs Private IP: The Difference and How to Check
What separates public and private IPs, how NAT and port forwarding relate, and how to check yours.
How to Get an SSL Certificate: Free Let's Encrypt to Paid Options
Free (Let's Encrypt/certbot) vs paid certificates, the issuance flow (CSR, validation) and auto-renewal.
Link Previews Not Showing (Kakao, Slack, X)? Fixing OG Tags
Why link previews are missing or stale when sharing, and how to fix OG tags and scraper caches.
Domain Expiry and Transfers: Process, Timelines and Gotchas
What happens when a domain expires (grace and redemption), how registrar transfers work, and staying online during one.
Cookies Explained: Session, Third-Party, Secure and HttpOnly
Cookie types (session, persistent, third-party) and what each security attribute — Secure, HttpOnly, SameSite — protects against.
Cache-Control Done Right: Making Browser Caching Work
What max-age, no-cache, no-store and immutable really mean, with recommended policies per resource type.
Slow Site? Diagnosing and Fixing TTFB Step by Step
Where time-to-first-byte goes — DNS, TLS, server, database — and how to diagnose and cut each stage.
Setting Up DKIM: Key Generation, DNS Records and Verification
How DKIM signing works, what selectors are, and the full flow: generate keys, publish DNS, verify.
Creating and Submitting sitemap.xml to Speed Up Indexing
Sitemap format, using lastmod correctly, how to submit to each search engine, and common errors.
Enabling gzip and Brotli: Cut Transfer Size by 70%
What compressing text resources buys you, nginx/Apache config, verification and common mistakes.