Steps to reproduce:
1) Navigate to https://hsivonen.com/test/moz/
In Safari 14.0 (14610.1.28.1.10) on macOS Mojave 10.14.6, Safari says:
Safari can't open the page. The error is: "The operation couldn't be completed. Protocol error" (NSPOSIXErrorDomain:100)
In Safari on iPadOS 14.1, the error message is:
Safari could not open the page because the server stopped responding.
Firefox and Chrome load the page just fine. The page is proxied by nginx with Apache as the origin server. The same nginx instance also serves https://hsivonen.fi/ (served from flat files by nginx itself) and https://html5.validator.nu/ (proxied by with Jetty as the origin server), and Safari can load these pages from the same nginx instance.
Expected the page to load.
This was resolved by adding
to nginx config per
I'm leaving the bug open due to the error message being very uninformative.
Thanks for filing. Safari error messages like these are handled outside of WebKit. Please file feedback at feedbackassistant.apple.com and reference this report. Thanks!