[jQuery] Increase / Decrease Font Size

[jQuery] Increase / Decrease Font Size


I am using the following code to allow the user to increase / decrease
the font size of the document. I have tested it in many browsers and
in all of the following it comes back with a starting font size of
16px.
Firefox 3.0.8
Google Chrome 1.0.1
Safari Win 4 Public Beta
In IE 6/7 the font size is always coming back 1243px. Why is there
such a difference and is there anyway to get around this besides hard
coding the starting size?
<script type="text/javascript" language="javascript">
$(document).ready(function(){
    var originalFontSize = getFontSize();
    $(".resetFont").click(function(){
        setFontSize(originalFontSize);
        $("#changeFont").fadeToggle("fast");
        return false;
    });
    $(".increaseFont").click(function(){
        var fontSize = getFontSize();
        var newFontSize = fontSize + 1;
        setFontSize(newFontSize);
        return false;
    });
    $(".decreaseFont").click(function(){
        var fontSize = getFontSize();
        var newFontSize = fontSize - 1;
        setFontSize(newFontSize);
        return false;
    });
});
function getFontSize() {
    var currentSize = $("html").css("font-size");
    var currentSizeNumber = parseFloat(currentSize, 12);
    if(currentSizeNumber > 20) {
        currentSizeNumber = 20;
    }
    return currentSizeNumber;
}
function setFontSize(size) {
    $("html").css("font-size", size);
}
</script>