Assertion:
Netscape 7.0+: For the BEHAVIOR attribute, the ALTERNATE value is rendered differently than IE - In IE, the marquee starts at one side of the marquee box, already onscreen. It then proceeds to the opposite side of the marquee box, until its leading content edge reaches the marquee box edge, and then returns back the way it came. In Mozilla, the marquee content starts offscreen, comes onscreen at one side, travels to the opposite side, then goes offscreen before travelling back the way it came.

Basic MARQUEE element, no width.:
filler text Marquee filler text

Basic MARQUEE element, no width, behavior=alternate.:
filler text Marquee filler text