How to reduce page loading time when we have to make several XMLHttpRequest simultaneously using jquery load statement?

Question

I have a template page named as 'career_new.php'. I want to use this template for my several pages related to different careers such as CA, Engineering, MBA etc. For this I have written the code which is appearing below this paragraph. This code is executing without any Error and showing all the content properly but it is taking too much time to load this page. Here is the code for my page ca.php :

<?php

     include_once 'career_new.php';// to include the main page (template page)

?>

<script type="text/javascript" src="js/jquery-1.7.1.min.js"></script>

<script type="text/javascript" src="changeContent.js"></script>



<script>

    $("#career_content").load("html_ar/ca_ar_1.html");// for main content

    $("#adv1").load("php/add_demo.php");// for advertisement

    $("#slider2").load("php/ca_link1.php");// for left hand side article list

    $("#Div3").load("html_ar/img_gal.html");//for right hand side image gallery

    $("#Div5").load("ph_link2.php"); // for right hand side external article list

    $("#Div7").load("php/ph_link3.php");// for bottom link1

    $("#Div9").load("php/ph_link4.php");// for bottom link2

    $("#Div11").load("php/ph_link5.php");//for bottom link3

</script>

What should I do to reduce the page loading time? I am checking it with internet connection of 2.0 mbps bandwidth and it is taking approximately 15 sec. to load the page which is too high as compare to standard time of 4s-6s. Please guide me in this regard.

Size of the template page (including all html,css,js and other image files is around 800 KB )