Why the animation is not saved?

I could edit and save the animation many times as gif, but now it does not work. I do the same, save the animation, nothing changed, but when I open it with Firefox, it doesn't show the movement, only a still image. :-O
Another question: I want to put in a little pause between the loops, but "Pause" has no effect. What can I do?

1. make sure you use File > Export Animation and not File > Export
2. Pause: Display this Frame for nn seconds in "Properties"