The Open Mobile Alliance, who are responsible for co-ordinating the web-browsing efforts of mobile phones, seem to have misplaced xhtml-mobile12-model-1.mod. This file is a key part of the DTD for the latest version of their XHTML Mobile Profile standard, which defines how authors should construct web pages intended for the consumption of mobile phones. Now that it’s missing, all pages that reference the XHTML Mobile Profile 1.2 DTD are instantly invalid. Oops!
Oh, and the corresponding files for versions 1.0 and 1.1 of the standard have also gone astray.