Ok, that error is not an error related to the .NET framework, but rather a problem with your configuration.
Things to check:
(1) In IIS, did you create a virtual directory for the site?
(2) In IIS, what version of the .NET framework did you select?
(3) In IIS, what 'rights' did you give the virtual director? Read Only? Read/Write? Read/Write/Execute?
(4) (Most important, I think) What are the Server premissions on the folder for which your site is located? Is impersonate = true? Does the ASP.NET user and IIS User have sufficient priviledges to access the site files?
The one thing I can tell you, however, is that it is in no way related to the installation of .NET on a client machine.