Netscape Navigator 3.01 or later and Internet Explorer 4.0 or later enable sound to be played without having to download a plug-in. (Netscape 2.02 and Explorer 3.0 require you to download this plug-in.) Browsers recognize HTML codes differently and you must type both codes for the sound to work in both browsers. This self-study monograph is cross-referenced between sections on Netscape Navigator and Internet Explorer. The Netscape Navigator section includes information on self-playing sounds and sound controls. Netscape supports .aiff, .wav, .au, and .midi sound formats. The Internet Explorer section includes information on self-playing sounds. (Controls are not supported at this time.) Explorer supports .wav, .au, and .midi sound formats.