function externalLinks()
{ 
	if (!document.getElementsByTagName)
	{
		return;
	}
	
	var anchors = document.getElementsByTagName("a"); 

	for (var i=0; i<anchors.length; i++)
	{ 
		var anchor = anchors[i];
		if (anchor.getAttribute("href") && anchor.getAttribute("rel") == "external")
		{
			anchor.target = "_blank";
		}
	}
}

window.onload = externalLinks;