If web.config contains a <httpHandlers> or <httpModules> section, that section must contain a <remove... /> or a <clear /> element.

This basically forces developers to explicitly enable inheritance in nested virtual directories. In 99% of cases this developers won't use inheritance on these two sections, however it causes issues when somebody wants to add a module or handler to the parent virtual directory.

<configuration>
   <system.web>
      <httpHandlers>
         <add verb="*" 
              path="*.New" 
              type="MyHandler.New,MyHandler"/>
         <add verb="GET,HEAD" 
              path="*.MyNewFileExtension" 
              type="MyHandler.MNFEHandler,MyHandler.dll"/>
     </httpHandlers>
   <system.web>
</configuration>

Figure: Bad example

<configuration>
   <system.web>
      <httpHandlers>
         <clear/>
         <add verb="*" 
              path="*.New" 
              type="MyHandler.New,MyHandler"/>
         <add verb="GET,HEAD" 
              path="*.MyNewFileExtension" 
              type="MyHandler.MNFEHandler,MyHandler.dll"/>
     </httpHandlers>
   <system.web>
<configuration>

Figure: Good example