<!DOCTYPE html>
<html>
<head>
<script src="/lib/jquery-1.12.2.min.js"></script>
<script>
$(document).ready(function(){
$(".btn1").click(function(){
$("#p1").animate({height: "+=20px"});
});
$(".btn2").click(function(){
$("#p1").animate({height: "-=20px"});
});
});
</script>
</head>
<body>
<button class="btn1">Animate +</button>
<button class="btn2">Animate -</button>
<p>This is a paragraph.</p>
<p id="p1" style="border:1px solid blue;">This is an animated paragraph.</p>
<p>This is a paragraph.</p>
</body>
</html>