Radomir,
Thank you for your valuable feedback. I wish I had better news, but coincidentally, I had checked these exact things prior to my post. Per your response, I just double-checked again -- everything is in order there.
The website is set to the app pool which is the only site using that pool. It is a "4.0 Integrated" pool. I also tried the auto-created pools for 4.0 upon installation of the 4.0 framework. There's one for "integrated" and one for "classic". I tried them both; neither works.
I tried running the app again (just to see if a good night's sleep for the server might make a difference) and received the same error:
Server Error in '/' Application.
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Configuration Error
Description: An error occurred during the processing of a configuration file required to service this request. Please review the specific error details below and modify your configuration file appropriately.
Parser Error Message: Unrecognized attribute 'targetFramework'. Note that attribute names are case-sensitive.
Source Error:
Line 10: during development.
Line 11: -->
Line 12: <compilation debug="true" targetFramework="4.0">
Line 13: <assemblies>
Line 14:
Source File: C:\inetpub\SiteData\mywebsite\web.config Line: 12
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Version Information: Microsoft .NET Framework Version:4.0.20506; ASP.NET Version:4.0.20506.1
The odd thing is that this same app runs fine on my local machine (which has 32-bit Vista Home Premium). It's just the server which gives this error (running Windows Web Server 2008).
Anyone have further thoughts before I go back to 3.5 Framework?