Problem with Using SQL Server Express user instancing under IISPosted: January 31, 2010
There is a security setting issue needs to be addressed if you want to run your web application which is created under your default document structure. For example, quoted from Microsoft: "c:\Users\[YourUserAccountName]\Documents\Visual Studio 20XX\Projects\[YourSolutionName]\[YourProjectnName]\App_Data\aspnetdb.mdf failed".
Just a quick note to the detailed document from Microsoft for resolving issues related to work with SQL Server Express instance for websites hosted under IIS6/IIS7/IIS7.5.
The document provided detailed instructions to resolve the issue.