Back in 1999 websites were fairly static, before embedded videos and Flash. Many still had excruciatingly slow dial-up connections to the internet, so file size had to be small. Some of us remember waiting hours to download one small image, and we still thought it was the coolest thing.
Thus the only practical way to use motion on a website was with the use of an animated GIF, about 10 kb in size. At HempNut, Inc. we used them to place banner ads for hemp foods. Here they are: