Most types of puzzles are on-topic here. You can read specific guidelines for puzzle types here
That link is: http://meta.puzzling.stackexchange.com/questions/3142/list-examples-of-things-you-think-are-on-topic-or-off-topic
Notice the domain is meta.puzzling.stackexchange.com instead of puzzling.meta.stackexchange.com.
Does that link even work? I get a HTTPS warning page from my browser.
Isn't it supposed to be puzzling.meta.stackexchange.com?
Thanks for pointing this out.
As bobble's answer already pointed out, this is detritus left over from earlier site reorganizations that shifted where the "meta" appears in the URLs. The old links should in fact work seamlessly, but the other possible issue is the original links on that page were all http://... instead of secure pages - and some browsers may have an issue with all the redirecting going on to take you to a secure page, for the updated "meta" URLs, and with whatever other canonicalization happens to URLs along the way. So, harmless, but annoying, and certainly unnecessary.
I've gone ahead and updated all the URLs on that Help page, making them https://... and using puzzling.meta.* instead of meta.puzzling.*
A while back, the move to HTTPS required shifting all X.stackexchange.com sites' metas to X.meta.stackexchange.com, from the old meta.X.stackexchange.com. While many areas of the site interface were updated to use the new links, /help/on-topic is one of the pages that site moderators can edit. Thus, I presume, it was considered unsafe to mass-edit all customized site help centers.
Though, since site moderators can edit that part of the help center, one of ours could go in and fix it. The above is more of a history lesson.
