I was recently browsing questions when this hover message appeared over my Top Bar:

JS failed to load

I have never seen it before, nor here or on other SE sites that I frequent. What purpose does that notification serves and why could it have appeared in this case?

I noticed that the notification stayed a while, and then after some time and hard refreshing my Firefox browser it went away, but I am still baffled at what could have caused this. Just now as I am editing this post I saw the notification again, and it went away just like the other one did.

Could it be my Internet connectivity (tbh it has been slower today than other days); has anyone else experienced this?


This happens when some of a page is served from one domain and some is served from another. For example, a page might be constructed with content from stackexchange.com, sstatic.net, googleapis.com, etc.

At least one of the domains was responding too slowly. That could happen for many reasons (such as that domain being blocked, the servers for that domain being down for maintenance or under heavy load, etc).

Many times, the problem is temporary or intermittent.

  • Thank you for your feedback, I had never experienced such problem. I guess my internet service was not optimal yesterday, so I suppose that was part of the problem. – DarkCygnus Oct 14 '17 at 18:57
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    @GrayCygnus - could be. A while back I had issues with a particular website (not this one) for a few days. Turns out one of the domains that housed some of their javascripts was suffering a Denial of Service attack. They brought the scripts in-house and the problem went away. – Joe Strazzere Oct 14 '17 at 19:55

I get it a lot because my internet is unreliable. Usually a refresh fixes it.

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    Yes, as I explained in the post I refreshed and it went away. But seems to solve the problem temporarily... seems to be inherent to the Internet connectivity right? – DarkCygnus Oct 13 '17 at 19:17
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    @GrayCygnus it's a connectivity/timeout problem – Richard Says Reinstate Monica Oct 13 '17 at 19:28
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    Yes, it's internet connectivity – Kilisi Oct 13 '17 at 19:45

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