There''s no generic method for web browser applications to access scanners, and it is not a scalable option in my opinion.

There are a couple of solutions, but they are unsecure, and rely on your clients only using Windows machines.

1. You can use ActiveX control - But that won''t work in all browsers.
2. You can''t use Windows Image Acquisition library directly from ASP.NET on the client side, since the code would run at the server.

Like Prasad wrote, web browsers do not support acquisition (scanning) features. This means to scan at the client side, the client machine must have components installed (such as ActiveX) that can be accessed from a web application.
Here''s an example of one way to do it using a Twain scanning library:
http://support.leadtools.com/CS/forums/18445/ShowPost.aspx