Please HELP ! Compiler Error Message: BC30466: Namespace or type HelloWorldobj for the Imp

Hi, i have created a class called "HelloWorldobj.dll". Yes, i compiled it with VBC.exe. And, no compilation error shown.

I have read an article on teaching people to run custome namespace/classes. It said that we can just create a folder called "bin" inside the web application folder, and put all the classes / calss file inside this "bin" folder.

Then, inside our code, what we need to do is just :
<%@dotnet.itags.org. Import Namespace="HelloWorldobj" %>
...
...
But, it can't work here!!! why? Error msg :

Compilation Error
Description: An error occurred during the compilation of a resource required to service this request. Please review the following specific error details and modify your source code appropriately.

Compiler Error Message: BC30466: Namespace or type 'HelloWorldobj' for the Imports 'HelloWorldobj' cannot be found.

Source Error:

Line 13:
Line 14: Imports ASP
Line 15: Imports HelloWorldobj
Line 16: Imports Microsoft.VisualBasic
Line 17: Imports System
Source File: C:\WINNT\Microsoft.NET\Framework\v1.1.4322\Temporary ASP.NET Files\hotelex\0fa6dfdb\85a29584\dehxro7g.0.vb Line: 15

I have tried it with another dll "Microsoft.Data.Odbc". it works!
<%@dotnet.itags.org. Import Namespace = "System.Data" %>
<%@dotnet.itags.org. Import Namespace = "Microsoft.Data.Odbc" %>
...
...

Really don't understand..

Can anyone teach me how to apply own class in ASP.NET?
What should i do or what should i set?Did you put the DLL in the application's root /bin folder?
Yes, i did. I have created a folder called "bin" inside my application folder.

Or, do u mind to tell me the step of start a new application? such as ,... what setting should do,.. where to configure,.. how,..
and especially those customer class file...

Or anyone can help?