Dreamweaver, like most browsers, can display both JPEG and GIF images. Dreamweaver, Microsoft Internet Explorer 4.0 and later, and Netscape Navigator 4.04 and later also support PNG images.
In general, JPEG is the superior format for photographic or continuous-tone images, and GIF is preferred for noncontinuous tone images or those with large areas of flat colors. The PNG format is a patent-free replacement for GIF that includes support for indexed-color, grayscale, and true-color images. It also provides alpha channel support for transparency. PNG is the native file format of Macromedia Fireworks.
To use an image as a page background, specify it as a page property. See Defining a background image or page color. To overlap images, insert them in layers. See Layers overview.