$(document).ready(function () {
    $(".zebratable tr").mouseover(function () { $(this).addClass("mouseoverColour"); }).mouseout(function () { $(this).removeClass("mouseoverColour"); });
    $(".zebratable tr:nth-child(even)").addClass("alternateevenColour");
    $(".zebratable tr:nth-child(odd)").addClass("alternateoddColour");
});