Partial update a list with AJAX

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Javascript

PHP

Ajax

MySQL

jQuery

I have a list from the database and I want to implement edit functionality where in onclicking a table column, the column becomes editable and on clicking out of column, the value gets updated.
I have used AJAX for this purpose. My code is as under:
Page1.php

<script src="http://code.jquery.com/jquery-1.10.2.js"></script>
<script>
function showEdit(editableObj) 
{
 $(editableObj).css("background","#FFF");
} 
function saveToDB(editableObj,column,id) 
{
 $.ajax(
 {
  url: "page2.php",
  type: "POST",
  data:'column='+column+'&editval='+editableObj.innerHTML+'&id='+id,
  success: function(data)
  {
   $(editableObj).css("background","#FDFDFD");
  }        
 });
}
</script>

The column of my table is as under:

<td contenteditable="true" onBlur="saveToDB(this, 'exmid','<?php echo $p0; ?>')"
         onClick="showEdit(this);"><?php echo $p3 ?>

Note: $p0 contains the serial no of row from mysql database table and $p3 contains the displayed text.
The code for page2.php is:

<?php
include_once 'includes/db_connect.php';
?>
<?php
$result = mysql_query("UPDATE examlist1 set " . $_POST["column"] . " =     '".$_POST["editval"]."' WHERE  sno=".$_POST["id"]);
?>

Problem: When i click on the column it becomes editable. Using alert() inside saveToDB() This is the first time I am trying to use ajax in a php code myself.
Plz suggest what is the problem and what is the solution. The code is being implemented on a Linux based server hosted at Godaddy using PHP 5.4
Also I would like to set the background color on fail. How to write it inside ajax block?

What I have tried:

I have checked that the function is called on clicking out of the column and also values of column and id are correct.
Then i tried the alert() function inside $.ajax and it was not called. I am not sure whether ajax is running or not.