As you migrate to Excel 2010 or 2013, you may sometimes encounter spreadsheets that open in a special Protected View mode. You can view - but not edit - such documents until you grant permission within an onscreen prompt. I'll explain Protected View and how you can adjust this security measure to suit your needs.
By default, Microsoft Excel 2010 and later assume that files opened from the Internet, e-mail attachments, or other certain locations could contain malicious programming code. Accordingly, Excel opens such documents in a special mode known as Protected View, which enables you to view, but not edit, the spreadsheet. You're notified of Protected View by way of the security prompt shown in Figure 1.
You'll notice that Excel's ribbon user interface is collapsed as well, since virtually all functionality in Excel is disabled except for navigating the workbook and copying selected cells to the clipboard. If you wish to edit the spreadsheet, you must click the Enable Editing button shown in Figure 1.