If you're thinking about adding video to your Web page, you should take a minute to learn about the different formats and embedding techniques available. Though it may be more convenient for you to work in AVI or QuickTime (because one or the other is native to your machine), the easy choice isn't always the best.
Let's start with a brief and very incomplete history of desktop video. After the success of QuickDraw (the technology that allowed Macs to display and print graphics along with text), Apple developed QuickTime as a video file format and multimedia architecture to handle "time-based" media. Introduced in 1991, QuickTime became the industry standard for desktop video production, and has yet to be eclipsed by any rival technology.
AVI (short for audio/video interleaved) is the video file-type used by Video for Windows, which is the multimedia architecture developed for Windows 95. AVI is supposed to play back faster and smoother than other formats by interleaving the audio data with every video frame. QuickTime, on the other hand, handles audio and video interleaving in larger blocks (half-seconds or seconds).
Both QuickTime and AVI are cross-platform compatible, though they require special playback software on non-native machines. You can create and view QuickTime files on a PC by installing QuickTime for Windows; it will integrate with the system and appear as a file option in video-editing programs. To bring AVI compatability to a Mac, install the Video for Windows Apple Macintosh Utilities.
So which one is better for the Web? My vote goes with QuickTime. AVI is great for integrating video into Word documents and PowerPoint presentations created on a Windows machine, but QuickTime's superior compression makes it better suited for the Web. And in that environment, any increased playback speed is nominal.
Compress, compress, compress
To avoid cursing yourself (or having your audience do it for you), you'll want to keep the file size as small as possible. This can be accomplished in two basic ways: reducing the frame rate (number of video frames displayed per second), and compressing the finished file.
Fluid motion in film and video is an illusion our eyes and brains play on us; Hollywood-style films and television broadcasts display about 30 fps (frames per second) to achieve fluid-looking motion. But you can run desktop video around half as fast, and have it look OK. As you're editing, you should play with the frame rate and aim for about 15 to 8 fps. For basic editing, if you can afford it, I recommend using Premiere Pro for Mac or Windows.
Keep in mind that a good audio track can go a long way toward distracting people from a low frame rate. Jerky sound is much more jarring than a discontinuous picture, so you shouldn't skimp too much on the audio. However, mono 8-bit sound at 22.05Hz is decent for music, and more than adequate for voice.
Compression is the next step, and I'd recommend using either Radius Cinepak or On2 Video to cut your file down to size. Aim for a mid to low Quality setting and one of the frame rates described above.