Something

var tds = document.getElementsByTagName("TD")
for(var i=0;i<tds.length;i++) {if(tds[i].className == "navigation") break;}
var first_td = tds[i];
var new_td = first_td.parentNode.insertCell(2);
new_td.className="navigation"
var new_a = document.createElement("A");
new_a.href = "/Hai2U.php"
new_a.textContent = "Hai2U"
new_td.appendChild(new_a);