web site and relative paths

I have a web site on local computer that is bound to a port 7070 and has a physical path as d:\Apath\Bpath. Inside of Bpath I have a web.config file. Everything works fine. I am trying to add another folder to Bpath to run a new JS application that will use backend from the current site. So, I am adding a folder to Bpath and trying to open a file from it as: http://localhost:7070/newfolder/commons/imgs/image.png

I am getting an error: HTTP Error 500.19 - Internal Server Error The requested page cannot be accessed because the related configuration data for the page is invalid.

Detailed Error Information Module ProtocolSupportModule Notification SendResponse Handler Not yet determined Error Code 0x800700b7 Config Error Cannot add duplicate collection entry of type 'add' with unique key attribute 'name' set to 'Access-Control-Allow-Origin' Config File \?\D:\Apath\Bpath\web.config

Requested URL http://localhost:7070/hewfolder/commons/imgs/image.png Physical Path D:\Apath\Bpath\commons\imgs\image.png

Last entry is wrong because newfolder folder is missed.

Seems like what I am doing is wrong. Is it?