字体显示大中小

<script type="text/javascript">
function fontZoomA(){
document.getElementById('fontzoom').style.fontSize='12px';
document.getElementById('fontzoom').style.lineHeight='26px';
allChanges("12px","26px");
}
function fontZoomB(){
document.getElementById('fontzoom').style.fontSize='14px';
document.getElementById('fontzoom').style.lineHeight='28px';
allChanges("16px","28px");
}
function fontZoomC(){
document.getElementById('fontzoom').style.fontSize='16px';
document.getElementById('fontzoom').style.lineHeight='30px';
allChanges("20px","30px");
}
function allChanges(_fontSize,_lineHeight){
var allSpan=document.getElementById('fontzoom').getElementsByTagName('span');
var allDiv=document.getElementById('fontzoom').getElementsByTagName('div');
for(var i=0;i<allSpan.length;i++){
allSpan.item(i).style.fontSize=_fontSize;
allSpan.item(i).style.lineHeight=_lineHeight;
}
for(var i=0;i<allDiv.length;i++){
allDiv.item(i).style.fontSize=_fontSize;
allDiv.item(i).style.lineHeight=_lineHeight;
}
}

</script>

字体显示：<a href="javascript:fontZoomC();">大</a> <a href="javascript:fontZoomB();">中</a> <a  href="javascript:fontZoomA();">小</a>