Set Homepage

i use this script for my web site and it doesnt work for setting it as homepage

function setHomepage() {
if (document.all) {
document.body.style.behavior = 'url(#default#homepage)';
document.body.setHomePage('http://www.www.com');

}
else if (window.sidebar) {
if (window.netscape) {
try {
netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");
}
catch (e) {
alert("this action was aviod by your browser，if you want to enable，please enter about:config in your address line,and change the value of signed.applets.codebase_principal_support to true");
}
}
var prefs = Components.classes['@mozilla.org/preferences-service;1'].getService(Components.interfaces.nsIPrefBranch);
prefs.setCharPref('browser.startup.homepage', 'http://www.www.com');
}
}

i cant find the error...can some one provide me with a working javascript for setting homepage

 

does this work in firefox... in fact the first one is the same as my script