ODBC for ASP.NET

I am using the Microsoft.data.ODBC.dll as a reference in
my project. Also, I do a few Imports in a VB class that I
have, so I can use the ODBCConnection, datareader,
dataadapter, etc... So far everything is good in my
development computer...

Problem:
when I move all the files to the live server I get error
"File or Assembly microsoft.data.ODBC was not found..."

Well, I decided to place the microsoft.data.odbc.dll in
the bin folder and it works, but honestly I don't even
know why.

Is that supposed to be there? If so, why it does not get
added when I compile the project?
Can someone give me some feedback because it is working,
but I really want to know more about this....

thanks,
jayuya