// Aktiver Link bleibt bleichfarbig
var currentItem = "link_1"; 
      function Navigation(Id) { 
             
            var CssClassActive = "active"; 
            var CssCLassInactive = "inactive"; 
             

            if(currentItem != "") { 
               document.getElementById(currentItem).className = CssCLassInactive; 
            } 
             
            // Neuem Item aktive Klasse zuweisen 
            document.getElementById(Id).className = CssClassActive; 
             
            // Neues Item merken 
            currentItem = Id; 
             
         }