Articles

Knowledge base on e-mail security, DNS, and domain configuration.

Robots.txt — a complete guide to the robots.txt file

Everything about the robots.txt file — syntax, directives, configuration examples, common mistakes, and SEO impact. A complete guide for webmasters.

SSL/TLS errors — what do they mean and how to fix them?

Meet the most common SSL/TLS errors: ERR_CERT_EXPIRED, NET::ERR_CERT_AUTHORITY_INVALID, SSL_ERROR_RX_RECORD_TOO_LONG, and others. Learn how to diagnose and fix them.

DNS errors — what do they mean and how to fix them?

Meet the most common DNS errors: NXDOMAIN, SERVFAIL, REFUSED, TIMEOUT, and others. Learn what causes them and how to diagnose them.

How to create secure passwords — online guide

Learn how to create strong and secure passwords, what to avoid, and how to use a password manager. Try our secure password generator online.

Text formatting styles – camelCase, snake_case and others

Learn the most popular text writing styles used in programming and SEO: camelCase, PascalCase, snake_case, kebab-case and others.

What is an IP address / IPv4 / IPv6?

Learn how to check your IP address, what the difference between IPv4 and IPv6 is, and how to check your location and internet provider.

HTTP Codes List

Complete list of HTTP status codes with descriptions — from 1xx to 5xx.

What is an SPF record?

We explain what SPF is and what individual record mechanisms mean.

The most common errors in SPF records and how to fix them

Learn why an SPF record may return a fail or permerror. We explain the most common issues and how to fix them.

DNS Records — A, CNAME, MX, TXT and other record types

Learn what DNS records are and how they work. We explain types A, AAAA, CNAME, MX, TXT, NS, PTR, SPF, DKIM, DMARC and what TTL and DNS propagation are.

HTML Headings H1–H6 — hierarchy, SEO and accessibility

Learn about H1-H6 tags and how a correct heading hierarchy affects SEO, WCAG accessibility and content structure. Find out how to avoid the most common mistakes.