I have used the following to create zoom button which work fine within Chrome but not Firefox.
<input type="button" value="A" ONCLICK="zoomin();" class="zoombutton" >
<input type="button" value="a" ONCLICK="zoomout();" class="zoombutton" >
<script language="JavaScript" type="text/javascript">
function zoomin(){
if(parent.parent.document.body.style.zoom!=0)
parent.parent.document.body.style.zoom*=1.2;
else
parent.parent.document.body.style.zoom=1.2;
}
function zoomout(){
if(parent.parent.document.body.style.zoom!=0)
parent.parent.document.body.style.zoom*=0.833;
else
parent.parent.document.body.style.zoom=0.833;
}
</script>
Thanks in advance