why i can't use attachEvent and innerHTML;

[SkyZhao]

if i use AttachEvent like this,it can't work;
eg:

var img = document.createElement("img");
img.appendChild("onclick",alert("test"));
var div = document.createElement("div");
div.appendChild(img); //can't work;
div.innerHTML="<-click this";


but i use attachEvent like this,it work;
eg:

var img = document.createElement("img");
img.appendChild("onclick",alert("test"));
var text = document.createElement("span");
text.innerHTML="<-click this";
var div = documet.createElement("div");

div.appendChild(img); //can work
div.appendChild(text);