The Graphics Internet Format (GIF) version 89a[11] is supported by almost all web browsers. Included in this format is an extension which allows several images to be stored in one image file and displayed sequentially as an animation. The animation sequence can repeat any number of times or repeat continuously until the user visits another web page. Web site developers use GIF animations as an easy way to add dynamic content to static HTML pages. Animations are also frequently used in commercial advertisement banners to provide the equivalent of television commercials in web pages. Whether it be a flashing logo or an advertisement, almost all of the popular web sites include at least one GIF animation.
Having animations in a web page can visually enhance a page, but along with them come a few problems. Since each frame in an animation is essentially a separate image, downloading an image with 10 frames is the same as downloading 10 separate images. Increasing the download time is a problem for modem users, where a single image would suffice. Another problem with GIF animations is that animations have the ability to specify the number of times the frames will be repeated. Not only can this number be very high it can also be set to the equivalent of repeating forever. Some animations also specify that there be no delay between frames. Combining repeating forever with no delay creates a GIF animation that can consume all the cpu resources of even a high-end workstation.
Netscape Navigator and Internet Explorer both allow GIF animations to be stopped by either pressing a key or clicking a stop button. While this does prevent animations from looping forever, the animation still must be downloaded in its entirety. Users still need to manually stop animations before they can cause problems.