My JS:
window.onload = function(){
if(/Android|webOS|iPhone|Windows Phone/i.test(this.navigator.userAgent)){
document.getElementById('datatable').style.fontSize = "10px";
} else {
document.getElementById('datatable').style.fontSize = "20px";
}
}
HTML:
<table class="TFtable" id="datatable">
...
</table>
Please note: there are currently no styles to do with font-size which are affecting class 'TFtable'.