buttons click not working

Hi,

I wrote to open popUp window on button Click in as3.

this is working local fine, but if i move to server(www.mainwebsite.com), button click working when i enter www.mainwebsite.com,

if i enter mainwebsite.com (without www) in address bar, that swf button click not working.

What is the reason?

bookmarks.addEventListener(MouseEvent.CLICK, bmClick);  
function bmClick(event:MouseEvent):void
{          var desiredURL:URLRequest = new URLRequest(javascript:NewWindow=window.open('http://api.addthis.com/oexchange/0.8/offer?url=http%3A%2F%2Fwww.somewebsite.com','newWin','width=400,height=300,left=0,top=0,toolbar=No,'); NewWindow.focus(); void(0););          navigateToURL(desiredURL, _self);
}