<script>
var isNav = (window.navigator.appName.toLowerCase().indexOf("netscape")>=0);
var isIE = (window.navigator.appName.toLowerCase().indexOf("microsoft")>=0);
function setFocus() {
    var range = this.createTextRange(); //建立文本选区 
    range.moveStart('character', this.value.length); //选区的起点移到最后去
    range.collapse(true); 
    range.select();
}

function onfocus() {
    if(isNav){
        document.getElementById('admin').focus();
    }else{
        setFocus.call(document.getElementById('admin'));
    }
 
}
</script>
<input id="admin" name="admin" value="test" type="text" />