I run fedora and use firefox. I also update my system weekly using yum. Recently I was testing something (directory linking) on my own local web using tomcat and one application.
I kept getting a total white screen with a particular test popup (using any of the 3 linking style and then even normal directories with NO linking). I tried the same application on another server using my local browser and got the same result. So I tried another machine with another browser and found NO problems - both my server or the other one did things right. Checking my version of firefox against that box, I discovered I was running v-25 versus it had v-26. I actually was fully up to date but had not brought up the new version of firefox after a system update (no warning was given to do so and no OS update so no reboot requirement was obvious). I killed firefox and tried to restart, but a reboot was required (firefox said it was still running - ??? - and yea a "kill -9" probably would have fixed that, but reboot is what I did). Anyway, after rebooting, ALL WORKED again - the blank white screens are gone. Apparently firefox was keeping something somewhere that made it fail with apache tomcat requests under certain conditions. The version running was confused as the next version was actually installed. This took me a couple days to find as I was not looking in the right places. I am just posting this in case anyone else has a similar problem.