why this don´t work:

function rp_insertTable() {
 FM_log(3,"rp_insertTable() called");
 var farmTable = dom.cn("table");
 var ftableBody = dom.cn("tbody");
 var i;
 var maximize = GM_getValue("Maximize_" + suffixGlobal, 0);
 farmTable.className = "FMtbg";
 farmTable.id = "farmMachineTable";
 farmTable.setAttribute('cellpadding', 2);
 farmTable.setAttribute('cellspacing', 1);
 farmTable.style.marginBotton = "12px";
 farmTable.style.font = "bold 12px arial,serif";
 farmTable.style.font = "bold 12px arial,serif";

the font does change in format, but the font size is not working, I can put 100px and it deosn´t change anything, why is that?