var limit = 20;  // max number of rows in total
var LIMIT=1;

function addRow(){

var content1='<input size="3" type="text" name="number[]" />';
var content2='<input type="text" name="title[]">';
var content3='<input size="10" type="text" name="aka[]">';


if (LIMIT == limit)  {
alert("You have reached the limit of adding " + (limit) + " inputs");
return false; // just leave
}

LIMIT++;

tabBody=document.getElementsByTagName("TBODY").item(0);
row=document.createElement("TR");
cell1 = document.createElement("TD");
cell2 = document.createElement("TD");
cell3 = document.createElement("TD");
cell1.innerHTML=content1;
cell2.innerHTML=content2;
cell3.innerHTML=content3;
row.appendChild(cell1);
row.appendChild(cell2);
row.appendChild(cell3);
tabBody.appendChild(row);
}