The Wiki Index with the different letters at the top doesn't actually work.
Looking at what it does with Firebug, it seems like the XHR is always being sent a parameter for view_args of 'a' and never the letter it has been clicked on.
Planescape, Dungeons & Dragons, their logos, Wizards of the Coast, and the Wizards of the Coast logo are ©2008, Wizards of the Coast, a subsidiary of Hasbro Inc. and used with permission.