I Audited 50 Websites. Here's What Was Silently Broken

I ran deep checks on 50 production sites. 23 had silent failures their uptime monitors missed. Here's every failure type, why it happens, and how to check yourself 1. Expired or Misconfigured SSL Certificates (8 sites) The most common failure — and the most avoidable. Eight sites had SSL issues. Three had certificates that had expired within the last 30 days. Two had incomplete certificate chains (missing intermediate CA), which meant the site worked in Chrome on desktop but threw security warnings in Safari and on mobile devices. The remaining three had certificates that didn't match the domain — likely from a server migration or load balancer change where someone forgot to update the cert. Why uptime monitors miss this: Most ping-based monitors hit the IP address or follow the first redirect. They don't validate the full certificate chain, check expiry, or verify that the certificate matches the domain. The server responds with 200, so the check passes. How common is this? According