Resolvoing the error "The file could not be uploaded into the Web Forms designer."

Q: I received the following error ("The file could not be uploaded into the Web Forms designer.") when I opened a VS project, but I don't remember making any changes to the form design or the HTML?

A: Try to compile the project and see if there's an error in the code behind file (i.e. .CS or .VB file). If there are errors resolve them, and you should be able to view the file.