Event.observe(window,"load",function(){
    var maxheight = 0;
    if(document.all) { //This means it is IE
        if($('subnav') != null){
            var subnav = parseInt(document.getElementById('subnav').offsetHeight);
            var subnavlist = parseInt(document.getElementById('submenu_list').offsetHeight);
            maxheight = (subnav>subnavlist)?(subnav):(subnavlist);
            var subnavheight=maxheight + 3 + 'px';
            $('subnav').setStyle({
                'height' : subnavheight
            });
            $('submenu_list').setStyle({
                'height' : subnavheight
            });
        }
    }
    else {
        if($('subnav') != null){
            subnav = parseInt(document.getElementById('subnav').getStyle('height'));
            subnavlist = parseInt(document.getElementById('submenu_list').getStyle('height'));
            maxheight = (subnav>subnavlist)?(subnav):(subnavlist);
            subnavheight=maxheight + 3 + 'px';
            $('subnav').setStyle({
                'height' : subnavheight
            });
            $('submenu_list').setStyle({
                'height' : subnavheight
            });
        }
    }
});