Where are you trying to download the GEDCOM from? A.com?
A GEDCOM file can only be read from a genealogy software program OR a text editor. DO NOT open a GEDCOM with a word processor it could destroy the file.
I use NotePad++ because it works with any text file,
If you are a Windows user you can try MS-NotePad but you will have to right click on the file and find the "Open With" option. MS-NotePad normally only open .txt file not .ged files
NotePad++ will present a list of files in its "Open" menu option.