Why do I get 800401F3 / 800A01AD errors?

This error is usually associated with trying to create an instance of a COM object using a ProgID that is not actually registered on the machine. The error message might be one of the following: 
 

Server object error 'ASP 0177 : 800401f3'   Server.CreateObject Failed   /<file>.asp, line <line>   Invalid class string     Server object error 'ASP 0177 : 800a01f3'  Server.CreateObject Failed  /<file>.asp, line <line>  Invalid class string    Microsoft VBScript runtime (0x800A01AD)  ActiveX component can't create object: <progid>  /<file>.asp, line <line>

 
Common causes for this are: 

1. forgetting to register the object using regsvr32;
2. fat-fingering the ProgID (e.g. "CDNOTS.NewMial");
3. not realizing that the object is not actually installed;
4. corrupted MDAC (see Article #2121;
5. using an MSWC or IIS sample component that is not installed (see KB #249290 for more info).

See Article #2135 for information on determining if a COM object is installed on your server. 
 
If you are getting the following error: 
 

Server object error 'ASP 0177 : 80080005'  Server.CreateObject Failed  /<file>.asp, line <line>   Server execution failed

 
See KB #241057 for information on setting your MTS package identity appropriately. 
 
If you are using Index Server, and this error occurs on the following line: 
 

Set something = Server.CreateObject("IXSSO.Query")

 
Then try the following, in this order: 

1. Make sure session state is enabled
2. Stop Index Service, empty the catalog.wci folder, restart the Index service
3. upgrade to version 3.0
4. uninstall / reinstall Index Server