Cannot add duplicate collection entry of type ‘add’ with unique key attribute ‘value’


Once I have transferred site from shared hosting to dedicated hosting and i got error “Cannot add duplicate collection entry of type add with unique key attribute value“.

see the below screenshot of error:

I have checked web.config file and IIS settings for this error.
I have seen below code in web.config file


This is for default document.

After that I have open IIS and check the site details, I have found below entries for the default documents:

So it occurs because of multiple entry of default page.

How can we solve it:To resolve this problem, first you must delete the duplicate entry that is defined at the highest level. The highest level may be the IIS server. After you delete the duplicate entry, the feature configuration page for the Web site or for the application should be displayed correctly.