Frequently there is an error navigating tag indexes, when you try to navigate to later pages of tag indexes (like http://libcom.org/tags/solidarity), where if you click "next" or a later page number, instead of taking you to the later page it just displays you a blank, slightly messed up index.
A workaround for this is that instead of clicking the link to take you to the later page, right click it and "copy shortcut" (or "copy link address" depending on your browser), then paste the URL into your browser address bar.
This will mean you can navigate the site properly.
But again, we hope to sort this problem out as well.
I'd love to know why this reappears time and time again.