Metatags
HTML tags that are not visible on a formatted page, but are used by search engines for indexing purposes.

MIDI
Musical Instrument Digital Interface. A format for sound data.

Mirror
An exact replica of a main site provided to users to improve accessibility.

Mouseover
Synonymous with rollOver.

MP3
MPEG1 Audio Layer 3. Audio file compression format with CD quality. A standard on the Internet.

MP3 Encoder
Software that converts Wave or AIFF sound files into MP3 format.

MPEG
Motion Picture Experts Groups. A set of norms for online broadcasting and compression of digital video and audio.

MusicMatch JukeBox
One of the most popular MP3 encoders on the Web.