- In Firefox, go to Tools > Options > Content, and make sure "[x] Load Images" is checked. Click [Exceptions] to verify if images from a specific domain are filtered.
- In SeaMonkey, go to Edit > Preferences > Privacy & Security > Images and check your "Image Acceptance Policy" settings. Click [Manage Image Permissions] to look for per-domain settings.
If you cannot install Adblock Plus or any other extension because it doesn't get activated after restart or you keep getting "Unexpected installation error -203", the extension files in your Firefox profile are corrupted. Go to your Firefox profile and remove the files extensions.cache, extensions.ini, extensions.rdf. These files will be created again when you start Firefox, and you should be able to install extensions then.
If you think you have found a bug in an older version of Adblock Plus, please try installing the newest version from http://adblockplus.org/en/installation first, it may be fixed already.
If the problem doesn't go away (yikes!), don't hesitate to report it here, feedback is very much appreciated.
Please include both your browser's and Adblock Plus's exact version number, your operating system (exact too. e.g. what windows) the language your browser is set to and - if existing - your filter list subscription(s).
In case the problem occurs on a specific website, please don't let us guess and share a link
If possible, also give the steps needed to reproduce the problem (e.g. "Open Adblock Plus Preferences, click Add Filter..., enter *kermit*, browser turns green and makes strange croaking sounds").
The output in the error console may help speed up debugging a lot:
In Firefox, go to Tools > Error Console, in SeaMonkey, go to Tools > Web Development > Error Console (the error console is called JavaScript Console in older browser versions) and copy & paste the error into your report.
Clearing the console's content before provoking the error may make it easier for you to find the right error messages.