When installing and running Office Excel 2013 on a host operating system where an Internet Explorer version earlier than IE9 apps will not work. Instead the the following error message will be displayed:

APP ERROR

Sorry, we couldn’t load the app because your browser version is not supported. Click here for a list of supported browser versions.

Link to Microsoft support site about supported browser versions.

Snippet from the page:

Apps for Office on the desktop

To host the apps for Office in the Word, Excel, Outlook, and Project desktop programs, use at least Internet Explorer 9 with at least MS12-037: Cumulative Security Update for Internet Explorer: June 12, 2012 installed.

The solution to this problem is to upgrade to a supported browser type and version.