HTML Attribute for <MARQUEE ...>
BEHAVIOR =SCROLL |SLIDE |ALTERNATE

BEHAVIOR indicates how the contents scroll.

BEHAVIOR=SCROLL, which is the default, indicates that the content should scroll off the edge of the marquee area, then reappear on the other side:

This Code Makes This
<MARQUEe BEHAVIOR=SCROLL>
Hello

BEHAVIOR=SLIDE is almost the same, except that it indicates that when the leading part content reaches the edge it should start over without scrolling off. notice in this example that the contents start scrolling again as soon as the "H" reaches the left side:

This Code Makes This
<MARQUEe BEHAVIOR=SLIDE>
Hello

BEHAVIOR=ALTERNATE makes the content bounce back and forth, all of it remaining visible all the time (assuming of course that it all fits).

This Code Makes This
<MARQUEe BEHAVIOR=ALTERNATE>
Hello

<MARQUEE SCROLLDELAY="..."> >