solution
function myFunction()
{
var table = document.getElementById("table");
var Row = table.insertRow(table.length);
var cell1 = NewRow.insertCell(0);
var cell2 = NewRow.insertCell(1);
var cell3 = NewRow.insertCell(2);
fname = document.getElementById("fname").value;
lname = document.getElementById("lname").value;
age = document.getElementById("age").value;
cell1.innerHTML = "fname";
cell2.innerHTML = "lname";
cell3.innerHTML = "age";
}