On the page https://math.stackexchange.com/help/notation, there are two links:
When I click on either of these links in Firefox, I get a message "Secure connection failed" with the error code SSL_ERROR_NO_CYPHER_OVERLAP.
The links work fine if I change "meta.math" to "math.meta":
Note that the title of the first link has apparently changed since the link was placed on the help page, so it redirects to
(I have not figured out how to coerce SE into showing the actual URLs instead of the names of the linked pages, but hovering over the link works.)