Why do I get 'Object doesn't support this property or method' errors?

Microsoft VBScript runtime error '800a01b6'   Object doesn't support this property or method: '<property or method>'   /<file>.asp, line <line>

 
Usually, this is because you used a property or method that doesn't exist, or doesn't exist in the version of the object you're using. For example, if you have MSXML 3.0 installed, and you try this code: 
 

<%      Set xmlhttp = CreateObject("MSXML2.ServerXMLHTTP")      xmlhttp.setRequestHeader "User-Agent","foo"  %>

 
Or if you are running IIS 4.0, and you try this code: 
 

<%      Server.Transfer "foo.asp"  %>

 
(See Article #2136 for more information on this scenario) 
 
And finally, if you tried to assign a variable to your own 'version' of an intrinsic object, e.g.:  
 

<%      response = "foo"  %>

 
In previous versions of IIS/ASP, this latter type of error can also lead to: 
 

Microsoft JScript runtime error '800a1390'  Illegal assignment    ' or     Microsoft VBScript runtime error '800a01f5'   Illegal assignment: 'someFunction'

 
Another possibility is that you forgot to use SET when assigning an object to a variable, e.g.: 
 

<%      set conn = CreateObject("ADODB.Connection")      conn.open "<connection string>"      rs = conn.execute("SELECT columns FROM table")      if not rs.eof then ' error here      ' ..  %>

 
The line starting with "rs = " should start with "SET rs = " ...