I've built an example below which should demonstrate my question:
Code:
<html>
<head>
<title>Test</title>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.6.4/jquery.min.js" type="text/javascript"></script>
<style type="text/css">
.hidden{
display:none;
}
</style>
</head>
<body>
<div id="container">
<div style="display:block" class="hidden">
test
</div>
</div>
<script type="text/javascript">
var contentStr = $('<div></div>')
$(contentStr).append($("#container").html());
alert(contentStr.html());
$(".hidden",contentStr).each(function(index){
	if($(this).is(":hidden")){
		alert("Hidden");
	}else{
		alert("Visible");
	}
});
</script>
</body>
</html>
Why is it that :hidden returns a value of hidden when the above value is visible. If I then remove the contentStr and grab it straight from the dom :hidden returns visible (as I would expect).

Does this happen because contentStr has not yet been added to the dom? If so, how can I check the visibility of the .hidden div correctly within contentStr.

Thanks for the help.