The file:
https://github.com/mongodb/mongo-csharp-driver/blob/gh-pages/2.6/apidocs/index.html
is being generated with an uppercase "I" and currently needs to be manually renamed.
The build script is supposed to be handling this:
https://github.com/mongodb/mongo-csharp-driver/blob/master/build.cake#L198
But it's not working.