var menu = document.getElementById("header").getElementsByTagName("div")[0].getElementsByTagName("ul")[0];

            for(i = 0; i < menu.getElementsByTagName("li").length; i++) {

                  var ul = menu.getElementsByTagName("li")[i].getElementsByTagName("ul")[0];

                  if(ul != undefined) {

                        ul.parentNode.onmouseover = function() {

                              this.getElementsByTagName("ul")[0].style.display = 'block';
                              this.className = this.className + ' hover';
                              
                        }
                        
                        ul.parentNode.onmouseout = function() {
                              
                              this.getElementsByTagName("ul")[0].style.display = 'none';
                              this.className = this.className.replace("hover", "");
                        
                        }

                  }
                  
            }

   }