I started a branch for doing W3C HTML validation on responses to zope.testbrowser requests: svn://svn.zope.org/repos/main/zope.testbrowser/branches/rossp-validator The idea is to be able to flip a switch and run all my functional zope.testbrowser tests and see validation failures as test failures. The current implementation in that branch just uses a simple environment variable since I wasn't sure what the best way was to support flipping a switch like that. Note that it's possible to use a local installation of the W3C validator (such as is available on Debian based systems in the w3c-markup-validator package) so that the validation doesn't actually slow tests down all that much. I have a couple of questions I'd like to hear any thoughts on. What's the best way to support "flipping the switch" in a global sense so that during the inner testing loop extra time isn't being wasted on repeated validations? Does this belong in zope.testbrowser or in the underlying mechanize package? Other than that, what's the path forward to merging? Ross