I am not sure why would you change the values on load.
Anyway, you can use jQuery onready function to change the cell values.
Something to start with:
<!DOCTYPE HTML>
<html>
<head>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>
<script>
$(document).ready(function() {
$(this).find("td").html("Hi");
});
</script>
</head>
<body>
<table>
<tr>
<td>Hello</td>
<td>Hello</td>
<td>Hello</td>
</tr>
<table>
</body>
</html>