How to implement the orange dialog SO used to notify user?

Question

Like "Please login or register to vote" and so on.

Answer 1

They use jQuery, specifically the functions fadeIn and fadeOut

Answer 2

1) CSS - make sure you can do the effect by editing the CSS source before you try to animate anything

2) Use mootools or jquery or something else to animate it on whatever event you want like so:

// mootools
$('flash_notice').tween('height',0);

// jquery
$('#flash_notice').animate({'height':0}, 500);