Asp.net code not running in server

Question

Hi,
In asp.net if we upload any code under App_code, the codes are automatically included in the project. We have uploaded Utility.cs file under dotnet/App_Code/BusinessLogic directory. After that when we create an object of that class, we got an error (http://www.find-villa.com/dotnet/index.aspx). We cannot understand why we get this error. We have used VS2008 for development. The code is running well in my local computer but when we upload all aspx cs, web.config files in server, we got this problem. Is there any problem in server configuration?
Best Regards,
Santanu