Problem mapping HttpHandler --> HTTP Error 404

Question

I am having problems trying to map an HttpHandler in the web.config.

This is the relevant config bit:

<httpHandlers>
  <add verb="*" path="*.hndlr" type="MyAssembly.MyHandler, MyAssembly" validate="false" />
</httpHandlers>

When I navigate to http://localhost/myApp/whatever.hndlr I am getting a server error 404 (not found).

It's the 1st time I am hooking up an HttpHandler so I might be missing something - any help appreciated!

UPDATE:

I managed to get it working using both answers so far - who's able to exaplin why it works gets the answer marked!

This is my config (won't work if Don't have both - I am running IIS7 in classic mode)

System.web:

<httpHandlers>
    <add verb="*" path="*MyHandler.hndlr" type="MyAssembly.MyAssemblyHandler, MyAssembly" validate="false"/>
</httpHandlers>

System.webserver:

<handlers>
    <add name="MyHandler" verb="*" path="*MyHandler.hndlr" type="MyAssembly.MyAssemblyHandler, MyAssembly" validate="false" modules="IsapiModule" scriptProcessor="C:\Windows\Microsoft.NET\Framework\v2.0.50727\aspnet_isapi.dll" resourceType="Unspecified" requireAccess="Script"/>
</handlers>

Answer 1

It is also possible to experience this error if you have set up the handler for 32 bit, but you are running in 64 bit (or vice versa). It's easy to set up both and have all the bases covered.

Note "preCondition", and "scriptProcessor" differences.

<handlers>
    <add name="MyHandler_32bit" verb="*" path="*MyHandler.hndlr" preCondition="bitness32" type="MyAssembly.MyAssemblyHandler, MyAssembly" validate="false" modules="IsapiModule" scriptProcessor="C:\Windows\Microsoft.NET\Framework\v4.0.30319\aspnet_isapi.dll" resourceType="Unspecified" requireAccess="Script" />
    <add name="MyHandler_64bit" verb="*" path="*MyHandler.hndlr" preCondition="bitness64" type="MyAssembly.MyAssemblyHandler, MyAssembly" validate="false" modules="IsapiModule" scriptProcessor="C:\Windows\Microsoft.NET\Framework64\v4.0.30319\aspnet_isapi.dll" resourceType="Unspecified" requireAccess="Script" />
</handlers>