Error: allowDefinition='MachineToApplication' beyond application level

Question

I've just encountered this "delight". It seems to present itself just after I've published a web application in release mode.

The only way to consistently get round the issue that I've found is to follow this checklist:

1. Clean solution whilst your solution is configured in Release mode.
2. Clean solution whilst your solution is configured in Debug mode.
3. Build whilst your solution is configured in Debug mode.

Just come across this post and that was happening to me.
Just Clean the project and the error goes away. (must be a VS2010 bug)

I have just had this problem when building a second version of my website. It didn't happen when I built it the first time.

I have just deleted the bin and obj folders, run a Clean Solution and built it again, this time without any problem.

None. You need to set up the directory you've placed the website as a web application within IIS.

This error occurs when you attempt to open a project as a website. The easiest way to determine if you've created a website or a project is to check your solution folder (i.e. where you saved your code) and see if you have a *.sln file in the root directory, if you do then you've created a project.

Just to add, I encountered this error just now when I attempted to open a project I created a while back by selecting "File", "Open Website" from the Visual Studio menus whereas I should have selected "File", "Open Project" instead. I facepalmed as soon as I realised :)