This goes in your API folder of Nancy + AppHarbor project - you DO NOT add anything to any other web.configs in the project to make it work

web.config

<?xml version="1.0"?>
<configuration>
	<system.web>
		<compilation debug="true" targetFramework="4.0" />
		<customErrors mode="Off" />
		<httpHandlers>
				<add verb="*" type="Nancy.Hosting.Aspnet.NancyHttpRequestHandler" path="*"/>
			</httpHandlers>
	</system.web>

	<system.webServer>
		<modules runAllManagedModulesForAllRequests="true"/>
		<validation validateIntegratedModeConfiguration="false"/>
		<handlers>
			<add name="Nancy" verb="*" type="Nancy.Hosting.Aspnet.NancyHttpRequestHandler" path="*"/>
		</handlers>
	</system.webServer>
</configuration>

Sweet gist bra