FireFox支持innerText

document.write(document.body.textcontent);

<script language="javascript">
function isie(){ //ie?
if (window.navigator.useragent.tolowercase().indexof("msie")>=1)
    return true;
else
    return false;
}

if(!isie()){ //firefox innertext define
    htmlelement.prototype.__definegetter__("innertext",
    function(){
        var anystring = "";
        var childs = this.childnodes;
        for(var i=0; i<childs.length; i++) {
            if(childs[i].nodetype==1)
                //anystring += childs[i].tagname=="br" ? "/n" : childs[i].innertext;
                anystring += childs[i].innertext;
            else if(childs[i].nodetype==3)
                anystring += childs[i].nodevalue;
        }
        return anystring;
    }
    );
    htmlelement.prototype.__definesetter__("innertext",
    function(stext){
        this.textcontent=stext;
    }
    );
}
</script>