i have been experiencing the same problems as mentioned in this threads.
Fedora20 wont open up yahoo or facebook, but it will open google and almost every other website
when i say doesnt load, i mean NOTHING, just a white page and the "page loading" going on forever. not even a "timed out" or error message
and it is ONLY on facebook and yahoo.
my wife's windows works fine on the same ISP
it doesnt work on any browser on my fedora (opera, firefox, seamonkey, chrome)
i dont know what to run to see identify the problem
one thing i have noticed, it happens on my verizon mifi, but at home (verizon/frontier) it works fine
but my wife's windows works fine on my verizon mifi
so i am thinking it may be something to do with fedora and verizon mifi (nothing but a guess)