centrum.cz

Readiness by lane

Green: centrum.cz. Thin bar: Webmail & Message Inboxes peer median.

Priority fixes for centrum.cz

Ordered by impact and by how common each practice is among peers.

1. Priority 1 · Harden

   HSTS kept for at least a year

   Observed: The homepage response did not include a Strict-Transport-Security header.

   Why it matters: HSTS tells browsers to use HTTPS for your host on every later visit, which removes the window where a first HTTP request can be intercepted.

   What to do: Send Strict-Transport-Security on HTTPS responses. Start with a short max-age (for example 300 seconds), confirm every subdomain works over HTTPS, then raise it in steps to 31536000. Add includeSubDomains only when all subdomains are HTTPS. HSTS preload is optional and hard to undo; hstspreload.org itself does not recommend it by default.

   On Cloudflare: Enable HSTS under SSL/TLS > Edge Certificates > HTTP Strict Transport Security and raise max-age gradually.

   61% of Webmail & Message Inboxes peers do this. Limit: Read from the homepage response only; other pages or regions may send different headers.

   Guide: HTTPS and TLS Guide for Website Owners

2. Priority 2 · Harden

   DMARC policy enforces quarantine or reject

   Observed: The DMARC policy for centrum.cz was p=none, which asks receivers to take no action on failing mail.

   What to do: Publish DMARC with p=none and a reporting address first, fix any legitimate senders that fail SPF or DKIM alignment, then move to quarantine and finally reject.

   58% of Webmail & Message Inboxes peers do this.

   Guide: A Practical Website Health Check for Owners

3. Priority 3 · Harden

   Framing restricted

   Observed: The homepage did not send frame-ancestors or X-Frame-Options, so other sites may frame it.

   What to do: Send Content-Security-Policy: frame-ancestors 'self' (or a list of trusted origins). X-Frame-Options: SAMEORIGIN covers older browsers.

   On Cloudflare: Add the header with a response header transform rule.

   76% of Webmail & Message Inboxes peers do this.

   Guide: A Practical Website Health Check for Owners

4. Priority 4 · Enable

   Canonical URL declared

   Observed: The homepage did not declare a canonical URL.

   What to do: Add a self-referencing canonical link to every indexable page, using the final https:// URL.

   52% of Webmail & Message Inboxes peers do this.

   Guide: Canonical Tags: A Decision Guide for Duplicate URLs

What centrum.cz already does well

Practices fewer than half of Webmail & Message Inboxes peers use.

• Structured data presentJSON-LD structured data found.24% of peers
• Reachable over IPv6IPv6 address published.27% of peers
• Certificate lifetime of 100 days or lessShort-lived 90-day certificate from Google Trust Services, already inside the 2027 limit.38% of peers

What we saw

Homepage checked

https://www.centrum.cz/

Homepage response

HTTP 200

TLS

TLSv1.3, HTTP/2

Certificate

Google Trust Services, 90-day validity, expiring 2027-01-10

CDN or edge

Cloudflare

Platform or framework

WordPress, Drupal, Next.js

DNS operators

Cloudflare

DMARC policy

p=none

Homepage HTML

1,528 KB, br

Images on homepage

190 (webp 295, jpg 80, svg 10, png 4)

Limits: homepage only, one location, one moment. Header checks reflect the homepage response; other pages may differ.

Stack and providers

Seen in the homepage response, certificate and DNS. Provider pages compare how their customers configure the same checks.

All 31 checks

Select a gap for the method and fix. How each check works

Compare with other Webmail & Message Inboxes sites

• emailondeck.com64
• freemail.hu41
• mailo.com58
• pec.it61
• serviciodecorreo.es46

Webmail & Message Inboxes readiness benchmark