How to change text content of Title tag using DOM?

programming web dev
1

Hi!
I have a title tag:
<TITLE>Title - Old</TITLE>
I want to change it to:
<TITLE>Title - New</TITLE>

I tried the following:
<BODY>
<SCRIPT>
var DocTitle = document.getElementsByTagName(“title”)[0];
alert(DocTitle.nodeValue);
</SCRIPT>
</BODY>

The alert box gives a message “null”(IE). Hence, am not able to access the title tag text node and hence am not able to change the contents! Any suggesstions???