Website putting out weird graphics!

[hessodreamy]

Twice in the last week my boss has told me that he's gone to our website and just seen "some kind of tartan design". This lasts a couple of minutes. He sent me a screenshot:
dodgy_screenshot.jpg

Needless to say, this is not what the website is supposed to look like.

I've not seen anything like this before. I can't see anything wrong in the server error logs. Apparently this only happens on our website, and only occasionally. I've told him to try a different browser next time it happens.

Any ideas what could be causing this? Some major error on the server? scrambled compressed output? corrupted browser cache?

I'm running php 5.3.15 on Apache Red Hat 2.2.3. Output is sent encoded with gzip.

[aaarrrggh]

Looks pretty bizarre to me. Are you creating any images dynamically or anything like that?

[Stevie D]

The first thing to check is whether you have an image that looks like that (or at least like one square of that) anywhere on your site.

[aaarrrggh]

The first thing to check is whether you have an image that looks like that (or at least like one square of that) anywhere on your site.

That's a good point...

If you can reproduce this bug in anyway, you could view the source in firebug to see what's going on. Could it be a small square image that only loads under certain conditions and is incorrectly sized in the <img> tag?

*Edit: can you provide a link to your website? If you don't want to send it publicly, feel free to pm me and I'll take a quick look to see if I can spot anything?

[hessodreamy]

There are no images dynamically generated. And that image doesn't appear anywhere on the site.
There are no server errors in the log.
Looking at the access log, I can see a request, which generated a 200 response and 13000 data and, a minute later, another request which also gave a 200 response and about 13000 (slightly different due to some randomised content). From the user's side, this first request gave the tartan, and the second one didn't. Also, both requests grabbed the main page and a couple of images and a stylesheet, so the browser obviously received a response, parsed it, then showed this!
aaarrrrggh, I'll PM you a link to the site.

[aaarrrggh]

I've sent you a private message. I think I've found the offending image, and because the site has conditional css that applies to IE 7 and below (and one css file that only applies to IE 6), I suspect the issue will be related to that image and most likely one of these css files...

*Edit: I sent him a link to the offending image via a private message.

**Another edit: Can you find out from your boss exactly which browser he was using? I suspect he was using IE 6 or 7. Can you confirm that?

Thanks

[hessodreamy]

I've sent you a private message. I think I've found the offending image, and because the site has conditional css that applies to IE 7 and below (and one css file that only applies to IE 6), I suspect the issue will be related to that image and most likely one of these css files...

*Edit: I sent him a link to the offending image via a private message.

**Another edit: Can you find out from your boss exactly which browser he was using? I suspect he was using IE 6 or 7. Can you confirm that?

Thanks

The browser being used was chrome, I'm afraid. But I had nothing to lose by removing the references to the conditional stylesheets, and the sprite image you mentioned. The issue was still there after multiple refreshes and even a cache clearout.
I got him to open IE9 while on the phone and that was looking fine.
Still confused...

[aaarrrggh]

Just sent you another pm...

[kduv]

What happens if you disable gzip compression on the site?