Unlike Macromedia Flash movies, you cannot right click GIF animations (or Cinemagraphs) and stop them from playing over and over in your browser.
Here's a very simple trick to prevent GIF graphics from animating in your web browser window - once the web page has stopped loading and GIF frames start to animate, just hit the ESC key on your keyboard.
That will immediately disable all the GIF animations on that webpage. In order to replay the animated images, you'll have to reload the page by pressing F5 or Ctrl+R.
How to Disable GIF AnimationsIf you want to permanently block GIF animations in your browser, do the following:
In Firefox - Type about:config and change the value of string image.animation_mode from normal to none.
In Internet Explorer - Tools -> Options -> Advance. Uncheck the box in Multimedia group that says "Play animations in web pages"
Also see: How to Make an Animated GIF