<script type="text/javascript">
if (/MSIE (d+.d+);/.test(navigator.userAgent)) { //test for MSIE x.x;
var ieversion=new Number(RegExp.$1) // capture x.x portion and store as a number
if (ieversion>=8)
document.write("You're using IE8 or above")
else if (ieversion>=7)
document.write("You're using IE7.x")
else if (ieversion>=6)
document.write("You're using IE6.x")
else if (ieversion>=5)
document.write("You're using IE5.x")
}
else
document.write("n/a")
</script>Referencia