The neatest thing I've found about css is the moz-opacity filter in Netscape andthe alpha filter in IE.
moz-opacity has a value between 0 and 1 while the alpha filter in IE (for windows only) is 0 to 100.
the syntax is as follows
filter: alpha(opacity=x); -moz-opacity: x;
where x is a value adherent to the conditions listed above
using the setTimeout method (function) one could fade in or out
aural style-sheets are soon to be implemented
-munchausen