You may apply Jquery like this Demo code:
<html>
<script>
$(document).ready(function(){
$("div.featuredposts_content1").hide();
$("div.featuredposts_content2").show();
})
</script>
<body>
<div id="IdOfDiv1" class="featuredposts_content1">
Cat1
</div>
<div id="IdOfDiv2" class="featuredposts_content2">
Cat2
</div>
</body>
</html>