Add 404 Not Found error page.
Remove custom 401 Unauthorised error page config.

We don't want to display an error page for this. Perhaps 403 Forbidden,
though.
Add 500 Internal Server Error page.

Awwww, headache puppy.
Add 403 Forbidden error page.

I'm sorry Dave. I'm afraid I can't do that.
Enable custom error redirect for 403 Forbidden.
Move error pages to their own folder.

Just tidy up a bit.
Redirect to InternalError.htm for all other errors

This is a pretty generic error page, actually, so just use this as the
default error page.
Fix the filenames for the custom errors.

They're all .htm files, not .html files.
Configure handler mapping for SVG images.
Ensure custom errors are displayed on Azure.

According to [this StackOverflow question and answer][1], the
configuration method I was using previously was insufficient, so configure
them at the web server level as well.

It seems that [this other thread][2] also provides part of the solution.

  [1]: http://stackoverflow.com/questions/10059009/enable-custom-errors-in-azure
  [2]: http://stackoverflow.com/questions/15144405/windows-azure-websites-is-overriding-my-404-and-500-error-pages-in-my-node-js-ap
More error page configuration...

Hopefully this will make them work? I'm clutching at straws a bit with
this one...
Merge branch 'feature/error-pages' into develop