I know how to switch to "Classic Mode" (from "Integrated Mode") in the full IIS via application pool settings. But I can't find how to do it in the current IIS Developer Express beta.
The MS Developer Express FAQ says it can be done, but not how. It's not in the WebMatrix GUI, as far as I can tell. Maybe customization of the Developer Express project file, but I don't see any documentation for that at all.
FYI, there is a Settings area where you can set SSL, CLR version (2.0 in this case), which is where I figure the Pipeline mode (Classic/Integrated) would be, but it's not there.