<script type="text/javascript" src="/js/jquery.js"></script>
<script type="text/javascript">
$(document).ready(function()
$(".btn1").click(function(){
$("#box").animate({height:"300px"});
$(".btn2").click(function(){
$("#box").animate({height:"100px"});
<div id="box" style="background:#98bf21;height:100px;width:100px;margin:6px;">
<button class="btn1">Animate</button>
<button class="btn2">Reset</button>