Changing Text Size as Zoom-in and Zoom-out Text using jQuery

<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js">
</script>
<script type="text/javascript">
$(document).ready(function() {
var divtxt = $('#fontdiv');

//Increase Font Size 
$('#btnincfont').click(function() {
var curSize = divtxt.css('fontSize');
var newSize = parseInt(curSize.replace("px", "")) + 1;
$(divtxt).css("fontSize", newSize + "px");
});

//Decrease Font Size 
$('#btndecfont').click(function() {
var curSize = divtxt.css('fontSize');
var newSize = parseInt(curSize.replace("px", "")) - 1;
$(divtxt).css("fontSize", newSize + "px");
})
});
</script>

<form id="form1" runat="server">
<div id="fontdiv">
Welcome to dotnetfunda.com.
</div><br />
<input type="button" id="btnincfont" value=" + " />
<input type="button" id="btndecfont" value=" - " />
</form>