Before CSS3 transition, we see loading spinners in flash website, and then AJAX component with animated GIF. Besides, animated GIF, we have seen VML & Canvas spinners too. Now, we have pure CSS animated loaders/spinners created with just HTML markup and CSS3.
Spinkit has a collection of good looking CSS spinners:
SpinKit uses CSS animations to create smooth and easily customizable animations. The goal is not to offer a solution that works in every browser. If you’re building a site with users running IE9 and below, you’ll want to detect support for the CSS animation attribute, and implement a fallback animation (e.g. a GIF.)
At the moment, it has 8 minimal and simple animated spinners ready to be used.