You have done lots of mistake.
you cant call multiple method or function like this on onclick event.
click by default submit the form.its mean it reloads static page again. ie. in its prev state. you have to stop submission of form.
here i have modified your code its working well. as per your requirement .
<script type="text/javascript">
$(document).ready(function(){
$("button").click(function(e){
var flag = confirm("Want to see the animation");
if(flag)
$(this).animate(
{
width: "70%",
opacity: 0.4,
marginLeft: "0.6in",
fontSize: "3em",
borderWidth: "2px"
}, 1500 ).fadeToggle("slow");
e.preventDefault();
});
});
</script>