window.onload = externalLinks;

function externalLinks() {
	if(!document.getElementsByTagName) return;
	var links,a,i;
	links = document.getElementsByTagName("a");
	for(i=0;i<links.length;i++) {
		a = links[i];
		if(a.getAttribute("class") && a.getAttribute("class").indexOf("extern") > -1) {
			a.onclick = function() {
				window.open(this.href);
				return false;
			}
		}
	}
}