Sharepoint loading assembly error in the event log

In my application event log window, I am getting this error:

Error: Failure in loading assembly: HelloWorldWebPart, Version=1.0.0.0, Culture=neutral, PublicKeyToken=9f4da00116c38ec5

 

This is caused by your web.config referencing assembly that doesn’t exists any more. The most likely cause is that you added HelloWorldWebPart as a safecontrol as part of a tutorial and then delete it later, but didn’t remove the reference.

The web.config is located at C:\Inetpub\wwwroot\wss\VirtualDirectories\<port number>. In most cases, the port will probably be 80. If you examine the web.config file, you may find the following reference:

<SafeControl Assembly=”HelloWorldWebPart, Version=1.0.0.0, Culture=neutral, PublicKeyToken=9f4da00116c38ec5″ Namespace=”HelloSpace” TypeName=”*” Safe=”True” />

 

Delete this reference and the problem will go away.