One of the impacts of moving to a fully XML friendly configuration is that many characters can no longer reliably be used for website, virtual directory and application names.
IIS has two basic constraints for these "path-sensitive" characters
The first is the characters that are not appropriate for HTTP URL's.
The second is the characters that are not appropriate for XML elements / configuration
So this means the following characters are dis-allowed by our UI:
? : @ & = , / \ < > " * |
However, our AhAdmin interface is more forgiving since it is not constrained by the way C# code interacts with XML, and there may be special circumstances where some of these characters will actually work. So if the UI blocks you from creating the item you need, try using tools such as appcmd.exe command-line tool or the AhAdmin COM interface.