Mastan Oli hit the nail on the head.

Here's how we do it:

Project.Web (UI)
Project.Controls (reusable .ascx controls, like GridView data)
Project.BusinessLogicLayer (code between UI/Controls to DataAccessLayer)
Project.BusinessObjectLayer (class object directly built from database tables)
Project.DataAccessLayer (code to access db)

We modeled this from Spaanjaar's series:  http://imar.spaanjaars.com/476/n-layered-web-applications-with-aspnet-35-part-1-general-introduction