Unable to open SharePoint 2013 site into SharePoint DESIGNER 2013

Issue
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While trying to open a SharePoint 2013 site using Microsoft SharePoint Designer 2013,
we get the below error message "The Server could not complete your request"

Cause
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Anonymous Authentication is disabled on the web application

 

Resolution
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Enable Anonymous authentication for the site from SharePoint.
We should enable it from SharePoint End rather than IIS web site