codice:
function showHideLayers(livello1,stato) {

                      if (stato == 'show') stato = 'visible';
                      if (stato == 'hide') stato = 'hidden';
                      theObj = eval("document.all['" + livello1 + "']");
                      if (theObj) {
                        theObj.style.visibility = stato;
                        theObj.zIndex = 10;
                      }
                
}

function drawMenu(){
//menu 1
                document.write("<div id=menuGen1 style='left:50px; top:0px; width:122px; height:15px; z-index:4; visibility: visible'  onMouseOver=\"showHideLayers('container1','show')\" onMouseOut=\"showHideLayers('container1','hide')\"><a href=\"#\"><font face=\"Verdana\" style=\"font-size:10px;\" color=\"yellow\">Il Nostro Gruppo</font></a>");
                document.write("<div id=container1 style='position:absolute; width:146x; height:40px; z-index:3; visibility: hidden;' onMouseOut=\"showHideLayers('container1','hide')\">");
                document.write("<TABLE BORDER=0 CELLPADDING=0 CELLSPACING=1 WIDTH=144 bgcolor=\"#0066FF\"><TR><TD BGCOLOR=\"#FFFFFF\">");
                document.write("<TABLE BORDER=0 CELLPADDING=0 CELLSPACING=2 WIDTH=142>");
                document.write("<TR><TD VALIGN=middle><div id=menu1_1 style='width:142px; height:18px'><A HREF=\"" + progurl + "/organigramma.php\"><font face=\"verdana\" style=\"font-size:12px;\" color=\"#000000\">Organigramma</font></A></div></TD></TR>");
                document.write("<TR><TD VALIGN=middle><div id=menu1_2 style='width:142px; height:18px'><A HREF=\"" + progurl + "/uc.php\"><font face=\"verdana\" style=\"font-size:12px;\" color=\"#000000\">Strategie</font></A></div></TD></TR>");
                document.write("<TR><TD VALIGN=middle><div id=menu1_3 style='width:142px; height:18px'><A HREF=\"" + progurl + "/storia.php\"><font face=\"verdana\" style=\"font-size:12px;\" color=\"#000000\">Storia</font></A></div></TD></TR>");
                document.write("<TR><TD VALIGN=middle><div id=menu1_4 style='width:142px; height:18px'><A HREF=\"" + progurl + "/tour.php\"><font face=\"verdana\" style=\"font-size:12px;\" color=\"#000000\">Tour Di Filiera</font></A></div></TD></TR>");
                document.write("<TR><TD VALIGN=middle><div id=menu1_5 style='width:142px; height:18px'><A HREF=\"" + progurl + "/uc.php\"><font face=\"verdana\" style=\"font-size:12px;\" color=\"#000000\">Eventi</font></A></div></TD></TR>");
                document.write("<TR><TD VALIGN=middle><div id=menu1_6 style='width:142px; height:18px'><A HREF=\"" + progurl + "/lavoraconnoi.php\"><font face=\"verdana\" style=\"font-size:12px;\" color=\"#000000\">Lavora Con Noi</font></A></div></TD></TR>");
                document.write("</TABLE></TD></TR></TABLE></div></div>");
                //menu 2
                document.write("<div id=menuGen2 style='top:10px; width:122px; height:15px; z-index:2; visibility: visible' ><a href=\"" + progurl + "/prodotti.php\"><font face=\"Verdana\" style=\"font-size:10px;\" color=\"yellow\">I Nostri Prodotti</font></a></DIV>");
                //menu 3
				document.write("<div id=menuGen3 style='top:30px; width:122px; height:15px; z-index:2; visibility: visible' ><a href=\"" + progurl + "/dove.php\"><font face=\"Verdana\" style=\"font-size:10px;\" color=\"yellow\">Dove Siamo</font></a></DIV>");
				//menu 4
				document.write("<div id=menuGen4 style='top:30px; width:122px; height:15px; z-index:2; visibility: visible' ><a href=\"" + progurl + "/sabellicommerciale.php\"><font face=\"Verdana\" style=\"font-size:10px;\" color=\"yellow\">Sabelli Commerciale</font></a></DIV>");
                //menu 5
				document.write("<div id=menuGen5 style='top:30px; width:122px; height:15px; z-index:2; visibility: visible' ><a href=\"" + progurl + "/uc.php\"><font face=\"Verdana\" style=\"font-size:10px;\" color=\"yellow\">Area Com. Interne</font></a></DIV>");
				//menu 6
                document.write("<div id=menuGen6 style='top:40px; width:122px; height:15px; z-index:2; visibility: visible' ><a href=\"http://80.207.33.22/\"><font face=\"Verdana\" style=\"font-size:10px;\" color=\"yellow\">Area Grossisti</font></a></DIV>");
                //menu 7
                document.write("<div id=menuGen7 style='top:30px; width:122px; height:15px; z-index:2; visibility: visible' ><a href=\"" + progurl + "/contatti.php\"><font face=\"Verdana\" style=\"font-size:10px;\" color=\"yellow\">Contatti</font></a></DIV>");
}

Come poso renderlo compatibile con firefox !?