Sometimes you may require visitors to wait for a while, for example, loading a flash animation, loading an external pages, etc… before something show up .During the waiting, this is better to show the progress to the visitors, otherwise they may wonder if your webpage hang up.
To see a demo, please take a look at my previous example of jQuery Fun with Animating Z-index of Div Layer. In this example I use a waiting GIF animation progress bar while the curtain is moving to the left.
I collected some Waiting GIF Animation Progress Bar on the Internet some years ago and using on some of my projects. Please use them carefully. I am not sure if they have copyright or not.
White Background Waiting GIF Animation Progress Bar
Transparent Background Waiting GIF Animation Progress Bar
Other Waiting GIF Animation Progress Bar
I will share with all of you if I find or make some Waiting GIF Animation Progress Bar in the future.