There are DOM inspectors in both IE and FF. In older IE versions you'll want the Document Tree section of their Web Developer Accessories. In IE8 there go to Tools->Developer Tools and there you have a nice little console to play with that will show you these things. In FF you can use the built in DOM inspector or Firebug (my personal favourite). There is also this bookmarklet, here is the code (cleaned up):
<html>
<head>
<script type="text/javascript">
var wer = "asdasd";
function getEm()
{
var x,d,i,v,st;
x=open();
d=x.document;
d.open();
function hE(s)
{
s=s.replace(/&/g,"&");
s=s.replace(/>/g,">");
s=s.replace(/</g,"<");
return s;
}
d.write("<style>td{vertical-align:top; white-space:pre; } table,td,th { border: 1px solid #ccc; } div.er { color:red }</style><table border=1><thead><tr><th>Variable</th><th>Type</th><th>Value as string</th></tr></thead>");
for (i in window)
{
if (!(i in x) )
{
v=window[i];
d.write("<tr><td>" + hE(i) + "</td><td>" + hE(typeof(window[i])) + "</td><td>");
if (v===null)
d.write("null");
else if (v===undefined)
d.write("undefined");
else
try
{
st=v.toString();
if (st.length)
d.write(hE(v.toString()));
else
d.write("%C2%A0")
}
catch(er)
{
d.write("<div class=er>"+hE(er.toString())+"</div>")
}
d.write("</pre></td></tr>");
}
}
d.write("</table>");
d.close();
}
</script>
</head>
<body onload="getEm()">
</body>
</html>