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For the past few days, I cannot see my avatar in any place where they use thumbs. I can see it on my profile page. But in the small info window on the top or in any of the questions or answers I posted, I just see the missing image question mark.

Not sure if this is a one-off thing or something's wrong with my id.

I can see everyone else's avatars fine!

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If upvotes are a way to say "me too", then, err, please at least comment "me too"? (You won't be the first and in this case I feel it's actually helpful.) –  Arjan Sep 19 '11 at 21:16
    
Me too! (But I was satisfied by the answer "It's yr browser", even though I can't figure how the fsck to get my browser (OmniWeb) to clear the cache just for that image.) @Arjan –  Josh Caswell Sep 19 '11 at 22:47
    
@Josh, see my edit, if you've not figured it out yet: when just showing the image by itself, hit Ctrl-F5 or Ctrl-Shift-R/Command-Shift-R, or hold down Shift when clicking the refresh button, to tell most browsers to reload unconditionally. –  Arjan Sep 20 '11 at 17:17
    
Thanks, @Arjan, but I can't tell you how many times I've tried Shift-Command-R and Shift-click. I've had this problem before; I think I may need to restart the browser entirely... –  Josh Caswell Sep 20 '11 at 17:22
    
Hmmm, @Josh, the Wikipedia browser-list doesn't show any clue for OmniWeb either. Odd! –  Arjan Sep 20 '11 at 17:25
    
Hmmm, I thought this was a dupe of Full-size avatar image updates, but thumbnail doesn't, but when trying to merge my own answers, things seemed to be too different after all. (This very question being about a cached, broken image, somehow.) I would revoke my close vote, if I could... –  Arjan Sep 20 '11 at 19:47
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1 Answer 1

up vote 4 down vote accepted

This is not a SE issue, but either a gravatar.com problem, some faulty caching proxy at your internet provider, or your own browser messing up.

So: test in another browser, or hit Ctrl-F5 or Ctrl-Shift-R / Command-Shift-R, or hold down Shift when clicking the refresh button, to tell most browsers to reload unconditionally. You might even need to clear all cache and restart your browser.

I can see yours just fine, at http://www.gravatar.com/avatar/c82255633259358535c704fa2ac05e93?s=32&d=identicon&r=PG, and so do Web-Sniffer and Imgur, both from a totally different location in the world.


As for the cause:

My bet is it's your own browser that has somehow cached a broken image. The browser doesn't know the response was faulty (if it would, it should not cache it). And it shows the question mark (or some other "broken image" icon) not because it cannot load the image URL, but because it cannot render the (cached) response as an image.

Peeking into the cache might even show you some other content type, like HTML rather than binary image data; <img src="http://stackoverflow.com/about"> would also show to indicate a rendering problem.

Gravatar tells browsers to only cache for 5 minutes, but browsers conditionally check for updates when reloading a page, also when a browser has somehow cached a broken image. For default (generated) images, Gravatar returns Last-Modified: Wed, 11 Jan 1984 08:00:00 GMT. A conditional reload then looks like:

GET /avatar/c82255633259358535c704fa2ac05e93?s=32&d=identicon&r=PG HTTP/1.1
Host: www.gravatar.com
...
If-Modified-Since: Wed, 11 Jan 1984 08:00:00 GMT
... 
Cache-Control: no-cache

...for which Gravatar responds:

HTTP/1.1 304 Not Modified

This tells your browser its cache is just fine.

The same can happen for non-default avatars, though those (used to) have their Last Modified date set to the date one first subscribed. When not changing the image at Gravatar, the same HTTP/1.1 304 Not Modified will surely be returned then. But changing it might nowadays change the Last Modified date, and then tell your browser that a new image is available, silently fixing the faulty cache.

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Thanks it is a browser/caching issue. Can see it fine in other browsers. –  lostInTransit Sep 20 '11 at 5:26
    
Yay.. it shows up again :) –  lostInTransit Sep 20 '11 at 5:33
1  
+1: I've seen this before and it went away if I restarted my browser. (I suspect that some browsers don't really believe cache control directives.) –  Donal Fellows Sep 20 '11 at 9:12
    
@Donal, it seems that actually caching a broken image is the culprit, after which a conditional reload makes Gravatar respond there are no changes; see my edit. Makes me wonder why a browser would not know the cached image is broken... –  Arjan Sep 20 '11 at 16:45
    
@lostInTransit, what browser was giving you problems? (Google Chrome is known to have a faulty cache every now and then. If it was Chrome, and if it happens again, it might be nice to know if its cache shows an odd RESPONSE_INFO_TRUNCATED.) –  Arjan Sep 20 '11 at 16:49
    
Oops, my memory is failing me... I wrote about this before. –  Arjan Sep 20 '11 at 17:51
    
I was having trouble in Safari. Chrome showed the avatar fine. –  lostInTransit Sep 20 '11 at 18:47
    
@lostInTransit: I encountered it in Safari, but it depends on which browser cached the bad data. (Browser installations don't share their caches.) I suspect that the real problem is that occasionally — rarely, but just often enough — we're getting bad responses from Gravatar (and browsers cache the fact that there was a problem, which seems odd to me). –  Donal Fellows Sep 25 '11 at 7:56
    
@Donal, I don't think the browsers understand the response was faulty, and are showing the question mark not because they cannot find the image, but because they cannot render it. As for the cache: that still thinks all is just fine. –  Arjan Sep 28 '11 at 19:53
    
@Arjan: Depends on what the response code was; if it was 2** yet bogus (and the cache control wasn't right; I don't know what the problem actually was) then that should indeed be stored and continue to cause problems. Caching a 4** would be Wrong. –  Donal Fellows Sep 30 '11 at 12:24
    
@Donal, if you ever see it in Safari again, then I've posted some debug steps at Why doesn't my picture show up on my user card in Safari? I'd assume that indeed a 200 OK was cached. Gravatar would have no need for 4xx I guess, though 5xx should not be cached either. The problem might not originate from Gravatar either; maybe some faulty proxy server or even a faulty internet connection could cause this? But indeed: I've only seen complaints from Safari so far... –  Arjan Sep 30 '11 at 15:07
    
@Arjan: I don't usually run through a proxy, either at home or work. Guess it'll at least have to wait until the next time I'm on a business trip (possibly longer). –  Donal Fellows Sep 30 '11 at 17:15
    
You're most probably right about the proxy, @Donal. But actually one never knows if an ISP is silently "helping" you without the need for any proxy settings in OS or browser. –  Arjan Sep 30 '11 at 17:35
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