In Ajax.Net user can call web service through JavaScript. The URL that will take the call is something like:

http://myserver/webservices/datafactoryservice.asmx/Ping

Normally IIS will take care of parse /Ping to PathInfo. But since CMS is using wildcard mapping and this causes some issues with IIS 5.x . This problem does not exist on IIS 6.x. It is that IIS 5.x does support fallback on unknown request. If you use a IIS 5.x as development computer you will need add one http handler that handle it.

1. Add one line in your web.configure under httpmodules section:
   <add name="EnableAmsxOnIIS5x" type=" WebServiceFix.FixAsmxCalls,WebServiceFix"/>
2. Unzip this file and put DLL under bin folder.

 Here is the source code to that handler.

Don't forget change function permissions in admin mode that allow users to call WebService.