function init() {
  activateMenu('nav1');
  activateMenu('nav2');
  activateMenu('nav3');
  activateMenu('nav4');
}
window.onload=init;
activateMenu = function(nav3) {
    /* currentStyle restricts the Javascript to IE only */
    if (document.getElementById(nav3) != null) {
        if (document.all && document.getElementById(nav3).currentStyle) {  
            var navroot = document.getElementById(nav3);
            /* Get all the list items within the menu */
            var lis=navroot.getElementsByTagName("LI");  
            for (i=0; i<lis.length; i++) {
                /* If the LI has another menu level */
                if(lis[i].lastChild.tagName=="UL") {
                    /* assign the function to the LI */
                    lis[i].onmouseover=function() {        
                        /* display the inner menu */
                        this.lastChild.style.display="block";
                    }
                    lis[i].onmouseout=function() {                       
                        this.lastChild.style.display="none";
                    }
                }
            }
        }
    }
}