Excel 2013 is a great tool and we are really enthusiasts over all new features and way it looks. However the first issues start when you download an Excel file from the web and try to open it. You will get error message –

“The file is corrupt and cannot be opened” in excel 2013

Just right click on the file to bring up the file properties dialog.  You should see an Unblock button on the General tab.

Microsoft seems to be overprotective and giving a missleading error message. I would prefer the office 2010 policy – it is own responsibility what you try to download and open.