lok105,
<!DOCTYPE HTML>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
.orange {
background: #FFCC00;
}
p:last-child {
cursor: pointer;
background: rgb(0, 153, 51);
}
</style>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.0/jquery.min.js"></script>
<script>
$(function(){
var s = 1;
$("body").on("click" ,"p:last", function() {
$(this).after($("<p/>", {"text" : "новая строка"+s++, "class" : "orange"}));
});
});
</script>
</head>
<body>
<p>Строка</p>
<p>Строка</p>
<p>Строка</p>
</body>
</html>