Unable to load referenced library - Where are DLL references stored in an ASP.NET App?

 I removed a DLL I didn't need from my BIN folder in an ASP.NET 3.0 web application. There is no "References" folder in my solution (I'm loading from IIS).
Once I deleted that DLL I get this message:
 Error    107    Unable to load referenced library 'C:\Sites\wt\bin\Anthem.dll': The system cannot find the file specified.    C:\Sites\wt\bin\Anthem.dll     
I search my solution for the term "Anthem" and found nothing. I did a file search of all files in my app directory and found nothing.
 Where is this little reference hiding??? 
 Thanks.
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