On Firefox 26 and newer, plugins.click_to_play is 'true' by default, so you no longer have to manually set it in about:config. However, this doesn't actually se

On Firefox 26 and newer, plugins.click_to_play is 'true' by default, so you no longer have to manually set it in about:config. However, this doesn't actually set all plugins to click-to-play, but rather enables the click-to-play subsystem. You can set Flash (or another plugin) to click-to-play by going to Tools->Add-ons->Plugins and selecting "Ask to Activate" in the drop-down box next to the plugin. I believe this is by default only the setting for Java.