This post can also answer the question ” how to fix the firefox error on centos/redhat linux”

Installing the flash player on centos/redhat linux seems to be very difficult sometimes. But the installation is quite simple . The flash player may not be installed automatically using firefox. While trying install firefox, you may get the error following error ” Firefox could not install this item because “install-0zr..rdf” (provided by the item) is not well-formed or does not exist. Please contact the author about this problem.”The Screeshot of error is provided. To fix this issue, you need to upgrade/install certain libraries using yum. I have mentioned the commands below.