运用JavaScript简单区分IE和firefox浏览器

<script language="javascript" type="text/javascript">

var init=function(){

var txt=document.all||document.getElementById

if(document.all){

alert("IE: /n"+txt); //Microsoft IE6.0 7.0

}else if(document.getElementById){

alert("FF: /n"+txt); //Mozilla Firefox,opera,Apple safari,Google chrome

}

}

window.onload=init;

</script>

<script language="JavaScript" type="text/javascript">

if ((navigator.userAgent.indexOf('MSIE') >= 0) && (navigator.userAgent.indexOf('Opera') < 0)){alert('你是使用IE')}else

if (navigator.userAgent.indexOf('Firefox') >= 0){alert('你是使用Firefox')}else

if (navigator.userAgent.indexOf('Opera') >= 0){alert('你是使用Opera')}else

{alert('你是使用其他的浏览器浏览网页！')}

</script>