Mozilla Plans To Remove Support For Firefox Complete Themes
AmiMoJo writes: Mozilla's engineers have announced the removal of Firefox complete themes as a way to lighten the browser core and remove a feature they don't see as heavily used any more. "Personas", or lightweight themes that are basically just wallpaper images, will remain. The Firefox community did not respond well to this piece of news, most seeing it as the engineers "chromifying Firefox." The change is part of Mozilla's Great-or-Dead initiative, which plans to simplify the Firefox codebase and remove features that are not popular.
Let's hope "video autoplay" is next!
about:config media.autoplay.enabled = false
There might be a UI method of getting to that but I couldn't find it in the five seconds I allocated to searching. Note this only stops HTML5 videos, but you really ought to have Flash set to click-to-enable (or disabled) for myriad other reasons.