Animating adding a table row (JavaScript + jQuery)

Try this

$(document).ready(function() {
    $("#row_" + (pos + 1)).removeClass("hide").addClass("show-row").hide().show('slow');
});

Try this:

function addRow(pos) {

    // Insert new HTML table row
    var tblObj = document.getElementById('questionTbl');
    var newRow = tblObj.insertRow(pos + 1);  

    // Add new table cells
    var newCell1 = newRow.insertCell(0);
    newCell1.innerHTML = 'one';

    var newCell2 = newRow.insertCell(1);
    newCell2.innerHTML = 'two';

    var newCell3 = newRow.insertCell(2);
    newCell3.innerHTML = 'three';

    var newCell4 = newRow.insertCell(3);
    newCell4.innerHTML = 'four';

    var newCell5 = newRow.insertCell(4);
    newCell5.innerHTML = 'five';

    var newCell6 = newRow.insertCell(5);
    newCell6.innerHTML = 'six';

    var newCell7 = newRow.insertCell(6);
    newCell7.innerHTML = 'seven';

    newRow.id = "row_" + (pos + 1);
    newRow.className = "hide";

    $("#row_" + (pos + 1)).switchClass("hide", "show-row");
}

$(document).ready(function() { ... } should be used when you need code executed as soon as the DOM is ready to be manipulated, basically the function passed to the ready function is executed on page load. The original jQuery code would never execute as the function was attached to the ready event after the ready event had already been fired.

http://api.jquery.com/ready/