The QA / Testing page is useful for ensuring apps work, and you have the latest version of browser technologies.
Auto Mode, like on any other page of D7, will run each of these items in order.
Default Browser Tests - these will open up each page in your system default web browser to test that specific browser technology. The exception being Qualys Browsercheck which will check your browser for outdated technologies and offer one-click update options where needed.
File Tests - This merely opens the default app for that file, and ensures that it will open properly. Note I use the latest format for Microsoft Office files. If they don't open on an older version of Office (XP /2003) you can install the Microsoft Office Compatibility Pack or "FileFormatConverters.exe" from Microsoft.com to update these older versions of Office to work with the newer (2007-2010) file formats.