Cannot Open Excel using Office Web App in SharePoint 2010

This workbook cannot be opened because it is not stored in an Excel Services Application trusted location – SharePoint 2010

One of my colleagues sent me an email saying that he is getting this error (see below) whenever he tried to open an excel workbook. I just clicked the same file in the same location and I am able to open it.

But when I click on the excel file drop down –> View in Browser then I also got the same error.

The text format of the error is:

1 2 3

This workbook cannot be opened because it is not stored in an Excel Services Application trusted location.   To create an Excel Services Application trusted location, contact your system administrator.

According to the error message, obviously we need to add the document library path to Trusted File Locations in the Central Administration. So we will see the steps here.
Step 1: Go to Central Administration –> Manage service applications under Application Management

Step 2: Then click on the Excel Services Application

Step 3: Click on the Trusted File Locations

Step 4: Just click Add Trusted File Location under Excel Services Application

Step 5: Add the document library url (OR file location) on the Address box and check the  Children trusted check box –> Click ok
Please note: Don’t use like http://server:1010/documentlibrary1/forms/default.aspx instead of http://server:1010/documentlibrary1

If you use SSL (Secure Sockets Layer)/HTTPS connections, just add  https:// on the address.