Merhaba. Asagidaki kodu header.php dosyasina kopyala yapistir yapiniz.
<script type="text/javascript">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.getAttribute("rel") == "nofollow" || anchor.getAttribute("rel") == "external nofollow" || anchor.getAttribute("rel") == "nofollow external" ) ) anchor.target = "_blank"; }}window.onload = function() { externalLinks();}</script>