Efeito de transição mostrar e esconder div

Faça algumas alterações no código abaixo:

<a href="javascript:animatedcollapse.toggle('cat')">
<b>Abre/Fecha div</b>
</a>
<div id="cat" style="display: none; " groupname="pets" speed="400">
Obrigado por ler. (CONTEÚDO QUE MOSTRA)</div>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js"></script>
<script type="text/javascript" src="http://static.tumblr.com/enpbtf0/a8olor0ey/animatedcollapse.js"></script>

<script type="text/javascript">
animatedcollapse.addDiv('jason', 'fade=1,height=80px')
animatedcollapse.addDiv('kelly', 'fade=1,height=100px')
animatedcollapse.addDiv('michael', 'fade=1,height=120px')
animatedcollapse.addDiv('cat', 'fade=0,speed=400,group=pets')
animatedcollapse.addDiv('dog', 'fade=0,speed=400,group=pets,persist=1,hide=1')
animatedcollapse.addDiv('rabbit', 'fade=0,speed=400,group=pets,hide=1')
animatedcollapse.ontoggle=function($, divobj, state){ //fires each time a DIV is expanded/contracted
 //$: Access to jQuery
 //divobj: DOM reference to DIV being expanded/ collapsed. Use "divobj.id" to get its ID
 //state: "block" or "none", depending on state
}
animatedcollapse.init()
</script>

Créditos do código:
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