Flash not working in Firefox on linux

i recently had an issue with successful playing youtube videos in my firefox browser on my debian linux machine. i previously installed the flashplugin-nonfree package to use as the flash plugin and everything worked fine for a while.

after googling around i came to the realization that the following packages

browser-plugin-gnash
gnash
gnash-common

were installed at some point and prevented the correct rendering of flash videos. so i removed the gnash packages with the following command.

aptitude purge browser-plugin-gnash gnash gnash-common


after removing the gnash packages, youtube and other flash videos began working again as expected.

so, how do i prevent gnash from being installed again and causing future problems. i found several interesting solutions, a few are listed at the bottom of this post. i decided to place a hold on the gnash packages (while uninstalled). below is the command i used.

aptitude hold browser-plugin-gnash gnash gnash-common


i've never used hold with apt before, so hopefully this will prevent any future installs of gnash. if anyone has a successful experience preventing specific packages from being installed, i would definitely like to hear your solution.

also check out:
http://tuxmark.blogspot.com/2013/11/update-flash-plugin-in-firefox-on.html


below are a few links i found while researching this issue.

http://www.debian.org/doc/manuals/debian-faq/ch-pkg_basics.en.html
http://askubuntu.com/questions/75895/how-to-forbid-a-specific-package-to-be-installed
http://serverfault.com/questions/17046/preventing-specific-packages-from-getting-installed-in-debian