function external_link(){
   var host_Name = location.host;
   var host_Check;
   var link_Href;

   for(var i=0; i < document.links.length; ++i)
   {
       link_Href = document.links[i].host;
       host_Check = link_Href.indexOf(host_Name,0);

//	if(host_Check == -1 && (document.links[i].href.search(/^(javascript|mailto):/i) < 0)){
	if(host_Check == -1){
           document.links[i].innerHTML
              = document.links[i].innerHTML 
                + "<img src=\"image/external_link.gif\" height=\"11px\" width=\"11px\" 
                    alt=\"[外部リンク]\" class=\"external_link\">";
	document.links[i].target="_blank";
       }

   }
}
window.onload = external_link;