You just don't give up, do you

..
But you have a good point. By default it is not "best practice" to decide for your user whether a site should open in the current window or new window. This is why a website will not validate if the source includes a target="". However, you should be able to do it of course, so I thought of a fix that also by-passes the W3C validator check

. I just uploaded a new built (just download from main site). The only updated file is ./lib/sitemap.php (overwrite your current one). What this does is add a rel="external" to each external link.
If you now add this Javascript to your template or external JS file, all rel="externals" will be translated into target="_blank".
<![CDATA[
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;
]]>
Hope this helps! Not the easiest solution, but as said: specifying targets is "not done" and therefore I can't make it a default option.
Cheers!
Xander.