关于td.appendChild(b);报HierarchyRequestError错误

Question

function readerTitle(titls,titlesID,agentNum){
    var agents=agentNum.split(",") ;
    var temp=0 ;
    var titles = titls.split(",");
    var titObj = document.getElementById(titlesID);
    for(var i=0 ; i<titObj.childNodes.length ; i++){
        var td = titObj.childNodes[i];
        td.innerHTML="";
        var b = document.createElement("b");
        if(i==0)
        {
           b.innerHTML = titles[i] ;
        }else{
            b.innerHTML = titles[i]+'<br/><span style="color:red">('+agents[temp++]+")</span>";
        }
        td.appendChild(b);