The problem#
Slashdot recently made a change to their ad code that made the site completely fail to load for me, showing the message
Failed to load website properly since html-load.com is blocked. Please allow html-load.com
and then blaming ad blocking:
This page could not be loaded properly due to incorrect / bad filtering rule(s) of adblockers in use. Please disable all adblockers to continue using the website. (click OK if you'd like to learn more)
I could see the page loaded just fine behind those messages, so it was obviously a lie. But the page continually reloaded if I tried to dismiss those pop-ups, so the site was unusable.
(Actually, this appears to have been disabled in the time it took me to write this blog post, so I guess this is no longer needed. Although it may be applicable to other websites using the same or similar mechanisms.)
The solution#
Install this user script. I have only tested it with Greasemonkey on Firefox so it require modification to work on other user script managers or browsers.