MIME type for .mxf was already added to web.config

Mendix already had a mapping for the MIME type .mxf to text/xml which leaded to problems when configuring IIS the website didn't want to load. the java script because the MIME type was duplicated. it was defined in the web.config in Mendix\3.0.0\runtime\mxclientsystem\ and was configured in the IIS. the solution to the problem was to delete line in web.config. my question is this normal?
1 answers

IIS has a system of inheritance which is not always clear. If you define this mime type on the top level, you don't have to repeat it on a sublevel. This often occurs when you copy the web.config to another folder.