Where do I put a .dll file?

In my Win Form development I have develop a .ddl file name link42dll.dll. I make a reference by these 2 statements for an external procedure:

[DllImport("link42dll.DLL")]
publicstaticexternint startit();
My question is where I put that file in the web form ASP.NET project in order to make a similar reference.
Thanks in advance,
ngungo

Create a folder named bin under your web application and place the dll fine in that folder.