The game constantly flickers (Opera, Firefox)
 

Opera:

Deactivate inline frames in the Opera settings and reload the game.

Firefox:

a) If the scrollbar on the right constantly flickers the addon "Script Blocker" might be the problem. Changing the settings of this addon will solve the problem. Simply allow Shakes & Fidget and its scripts.

b) If the addon "Adblock Plus" is installed on your system open its settings and deactivate the Adblock for .sfgame.