        /*search for elements with a certain atrribute:*/
          file = elmnt.getAttribute("w3-include-html");
          if (file) {
            /* Make an HTTP request using the attribute value as the file name: */
            xhttp = new XMLHttpRequest();
            xhttp.onreadystatechange = function() {
              if (this.readyState == 4) {
                if (this.status == 200) {elmnt.innerHTML = this.responseText;}
                if (this.status == 404) {elmnt.innerHTML = "Page not found.";}