Block users script, confuse about it. Options

[emerika66]

<!-- begin code provided by createblog.com --><br /><!-- begin code provided by createblog.com --><br /><!-- Part II of Block Users Script submitted by http://www.xanga.com/home.aspx?user=sherrys_designs --><br /><script language="javascript"><br />function getXName() {<br />for (var i = 0; i < document.links.length; i++) {<br />if (document.links[i].href.substring(0,38)=="http://www.xanga.com/private/home.aspx") {<br />var link = document.links[i];<br />var text = document.all ? link.innerText : link.text ? link.text : '';<br />return text;<br />break;<br />}} <br />return null;<br />}<br /><br />xName = getXName();<br /><br />if (xName == 'USERNAME' || xName == 'USERNAME' || xName == 'USERNAME') {<br />alert("Sorry, you are either blocked from this site or not logged in.");<br />redirect();<br />}<br /><br /></script><br /><!-- end code provided by createblog.com --><br /><!-- end code provided by createblog.com -->

im still confuse of what to do even when i read the instructions,like how do i block unregistered users and people i dont want viewing in which part of the code