In 1989 Compuserve released GIF89A, an enhanced version of the popular GIF image format which allowed a sequence of frames to be stored as a single image and played by supporting software.
The GIF format was already popular on what passed for the Internet in those days (remember, the World Wide Web didn't even exist until 1991) due to its small file size, lossless compression, and wide support. The enhanced version, which allowed animations that anyone could create themselves provided they had supporting software, quickly became popular also.
In addition to animated GIFs, browser vendors added support for proprietary HTML elements that handled animation natively, such as the <blink> and <marquee> elements, which added different animated effects to text.
Neither of these elements was particularly attractive or successful and the W3C, as well as leading industry accessibility and usability experts, advised against their use in most cases. Different browsers at the time supported one or the other of these elements but not both. Both elements were added by their respective vendors as part of the original browser wars.
In the late 1990s, popular browsers added support for a technique known as Dynamic HTML (DHTML), which allowed scripting languages to modify the contents of a page after the page had loaded. DHTML wasn't any single technology, but rather a collection of techniques (JavaScript, CSS, the DOM, and so on) that worked together to enable a basic level of interactivity and/or animation.
In fact, DHTML made it possible to create quite advanced animations, but restrictions in the early implementations of the required technologies, as well as hugely varying browser support, made DHTML tricky at best.
This era also saw the release and rise of Flash (and Shockwave, a competing technology that was eventually subsumed by Macromedia), a vector and raster graphics format that allowed audio and video streaming, frame-by-frame animation, and a host of other features. Flash quickly became popular and at the time of writing is still the number one format for web-based video, browser-based gaming, and advertising.
Gradual standardization of the DOM across (most) browsers, as well as the rise of JavaScript libraries such as jQuery, which abstracted away the differences that remained between browsers, have opened up animation to a much wider range of people than ever before. The term DHTML isn't often used these days because of its connotations with poor support between browsers, but the underlying principles and techniques that drive many interactive and animated sites remain similar.
Today, in addition to the animations made plausible and accessible by JavaScript libraries we have much newer, much more exciting possibilities with CSS3 and native HTML elements such as the <canvas> element, which provides complete pixel-level control over an area of the page. We'll be looking at some CSS3 animation techniques, as well as the <canvas> element in more detail towards the end of the book. Flash-based animation is on the decline for the first time this century, and new technologies are poised on the horizon.