Most WordPress caching plugins cache the entire page, without an option to exclude certain parts of pages. Therefore, since a new anti-spam image entry is supposed to be generated upon every page load, a completely cached page will show old, and potentially expired anti-spam images. Therefore, this plugin adds an option to have the anti-spam image entry generated by JavaScript, thus bypassing the plugin system.

Of course, the drawback if you use that option is that visitors *must* have JavaScript enabled to be able to comment.

Download the 3.1.1 release on the plugin page, as always:

http://www.theblog.ca/anti-spam

If you have a question not related to this specific release, please start a new topic.