Microsoft HTML Help supports a wide variety of image formats, multimedia files, and effects.
.JPG, .JPEG (Joint Photographic Expert Group)
.GIF (Graphic Interchange Format):
.BMP (Windows Bitmap)
HTML Help also supports image maps (similar to WinHelp's hotspot images). This type of image contains graphical links to other topics. The clickable areas in the image are referred to as the "hotspots." When users click these hotspots, the HTML Help viewer displays the target topic. HTML image maps are actually a set of files that work together - mainly the image file and a Map file that defines the clickable areas and their associated targets (topics).
.AVI
.AU
.MID
.RMI
.WAV
Animated .GIFs
Other formats available on the Web such as Dynamic HTML (allows you to overlay different parts of the topic to create exciting 3-D effects) and Marquees (an area in a topic that displays a horizontally scrolling text message.