Speaking of non-conformant, I've encounter issues with CloudFlare CDN that its refuses to deliver the resources (IMG, JS, CSS, and so on...) if I were using New Moon,
but they do it just fine if I were using different browser, but I did not like using those browsers.
So I trying to override the User-Agent but the result were the same, such CDN very likely checking for something else. It took me quite a while to find out that what being checked were Referer.
I didn't knew when it started, but its seem that more-recent browser engine new-default behavior would not send full referrer URL if the requester hosts did not match target hosts.
In the picture below that would "www.manganelo.net" and "img-r1.2xstorage.com".
CloudFlare very likely using that as an excuses to ban services to ""older browsers"" that did not conforms.
Is there any setting in about:config or extension that I could use, so I did not have to open Inspect Elements & View Page Source every time such issues occurred, while I'm waiting for the New Moon updates?