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; 

function toggle_visibility(id) {
       var e = document.getElementById(id);
       if(e.style.display == 'block')
          e.style.display = 'none';
       else
          e.style.display = 'block';
    }