Call the script like this

<script src="jquery-1.4.min.js" type="text/javascript"></script>
<script type="text/javascript">
$(function() {
//show resize buttons
$('.resizers').load('setFontSizeComponent.html');
});
</script>

This is the code of the inserted component

Look at the script here.

<span class="font-label"></span> <a href="#" class="fscSmall bh_decreaseFont">A</a><a href="#" id="resetFont" class="fscMedium bh_resetFont">[A]</a><a href="#" id="increaseFont" class="fscBig bh_increaseFont">A</a>
<style type="text/css">
.fscSmall {
font-size:0.8em;
}
.fscMedium{
font-size: 1em;
}
.fscBig{
font-size: 1.2em;
}
</style>
<script src="jquery-1.4.min.js" type="text/javascript"></script>
<script src="jquery.cookie.js" type="text/javascript"></script>
<script type="text/javascript">
//load the font-size cookie if it exists and change body font
var currentFontSize = $('html').css('font-size');
var currentFontSizeNum = parseInt(currentFontSize, 10);
$.originalFontSize = parseInt($.cookie('fontsize'),10) || currentFontSizeNum;
$('html').css('font-size',$.originalFontSize + 'px');
$('.font-label').text('Size: ' + $.originalFontSize);

// Reset Font Size
$('.bh_resetFont').click(function(event){
event.preventDefault();
fsCResizeText(0);
});

// Increase Font Size
$('.bh_increaseFont').click(function(event){
// prevent url
event.preventDefault();
fsCResizeText(1);
});

// Decrease Font Size
$(".bh_decreaseFont").click(function(event){
// prevent url
event.preventDefault();
fsCResizeText(-1);
});

/**
* resize html base font size. when 0 value is passed the original fontsize on start of the page is reset
* @addition{integer} number to increase the fontsize
*/
function fsCResizeText(addition) {
var newFontSize;
if (addition == 0) { // reset size
newFontSize = $.originalFontSize;
}
else {
var currentFontSize = $('html').css('font-size');
var currentFontSizeNum = parseInt(currentFontSize, 10);
// set fontsize between 8 and 20 px
newFontSize = Math.max(8,Math.min(20,currentFontSizeNum+addition));
}
$('html').css('font-size', newFontSize);

// Create (or update) the value of a cookie:
$.cookie('fontsize', newFontSize);
$('.font-label').text('Size: ' + newFontSize);
}
</script>