Here is the code needed to run HTML pages with asp.net. Add it to the Web.Config.
The code comes from this post:
http://forums.iis.net/p/1158398/1907100.aspx
<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<system.webServer>
<handlers>
<add name="ASPX-HTML-Integrated" path="*.html" verb="GET,HEAD,POST,DEBUG" type="System.Web.UI.PageHandlerFactory" preCondition="integratedMode" />
<add name="ASPX-HTML-2.0-Classic-32bit" path="*.html" verb="GET,HEAD,POST,DEBUG" modules="IsapiModule" scriptProcessor="%windir%\Microsoft.NET\Framework\v2.0.50727\aspnet_isapi.dll" preCondition="classicMode,runtimeVersionv2.0,bitness32" responseBufferLimit="0" />
</handlers>
</system.webServer>
<system.web>
<compilation>
<buildProviders>
<add extension=".html" type="System.Web.Compilation.PageBuildProvider" />
</buildProviders>
</compilation>
<httpHandlers>
<add path="*.html" type="System.Web.UI.PageHandlerFactory" verb="*" />
</httpHandlers>
</system.web>
</configuration>