img-swap.html

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN">

<html>
<head>

        <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.4.4/jquery.min.js" type="text/javascript">
</script>

        <title></title>
</head>

<body>
        <script type="text/javascript">
        $(document).ready(function() {
                function addAfterB(pElement) {
                        if (!$('#b ~ p')) {
                                $(pElement).insertAfter('#b');        
                        } else if ($('#b ~ p')) {
                                $('#b ~ p').remove();
                                $(pElement).insertAfter('#b')
                        }        
                }
                addAfterB('<p>New Item 1</p>');
                
        });
        </script>

        <div id="a">
                <div id="b"></div>
                <p>hello</p>
        <div>
</body>
</html>