check the users permission to access that file.

If you dont know how to see who is running just open the web app inside the IIS console and on the Anonymous tab you click the top button and it will show you the current user.

Also you might have impersoantion set in the web.config file.

But, the answern is simply the folder where the file doesn't does not have persmission for that user

Anything written be Dino Esposito is excellent. He has tons of articles on MSDN and has written a handful of books

Well actually winforms development takes longer for several reasons. Ever customize a data grid? Thats anywhere from 80 to 2k lines easy.

Most new tools are made for ASP.NET, so there is a lot of custom programmingm for WebForms. You have to manage thread state with controls. For instance, developing a tree view on a separate thread is a nightmare.

Where as asp.net has many, many new tools and we work on a common thread...