This workbook cannot be opened because it is not stored in a trusted location - SharePoint 2010 / 2013

If you are facing the following error:
This workbook cannot be opened because it is not stored in a trusted location. to create a trusted location, contact your system administrator

then here is the resolution: 
http://sharepointknowledgebase.blogspot.com/2011/12/this-workbook-cannot-be-opened-because.html