If you’re a O2 customer using Firefox to browse the Internet there’s a fix for the O2 image compression they force upon your on their mobile broadband. You can perform the follow configuration of Firefox to get normal images:

1. Install Modify Headers add on.
2. On the Modify Headers screen add the following new names and values:
NAME:Pragma VALUE:no-cache
NAME:Cache-Control VALUE:no-cache
3. Click on the configuration button and select the always on option.

Original forum thread. Thanks to @asimoa for providing this fix.

This, unfortunately, only improves your viewing experience in Firefox. Images in other applications are still in poor quality.

[Update] Fix for O2 iPhones.

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