??? What the heck did you do ??????
that is a custom FEDORA20 repo
you can NOT use a fedora repo file on cent !!!!
REMOVE IT ASAP !
that is at least part of the problem
the other is you have ZERO software repos installed
besides the very incompatible thing
that looks like a html document you renamed to .repo
there should NEVER !!!
be a php encoded HTML header
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
in a repo file
just HOW ?????
did you manage to do this ?
as in what did you do ?
this is the current cent 6.x repo listing
after you remove that think pretending to be a software repo text file
manually install this rpm using rpm
in the firefox download dialog there is a option to INSTALL it
install it !