basic JQuery marginTop help needed
<p>Can anyone tell me what im doing wrong! Trying to make the navigation and logo to move up when a menue is clicked. I will then show the content below the new position of the nav. I am simply doing this by changing the value of the marginTop. </p>

<pre><code>&lt;!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"&gt;
&lt;html&gt;
&lt;head&gt;
    &lt;meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"&gt;
       &lt;title&gt;****&lt;/title&gt;
    &lt;link href="design/style.css" rel="stylesheet" type="text/css"/&gt;




&lt;/head&gt;
&lt;body&gt;
    &lt;div id="headingBlock" style="margin-top:140px;"&gt;
    &lt;div id="logo"&gt;
    &lt;a href="index.html"&gt; &lt;img src="design/images/pmb_logo.png" alt="****"/&gt;
    &lt;/a&gt;
    &lt;/div&gt;
    &lt;/div&gt;

&lt;div id="navStrip"&gt;
    &lt;div id="navBlock"&gt;
    &lt;div id="nav"&gt;
        &lt;a href="index.html" id="midPage"&gt;Home&lt;/a&gt;
        &lt;a href="#" class="topPage"&gt;Our Homes&lt;/a&gt;
        &lt;a href="#" class="topPage"&gt;Displays&lt;/a&gt;
        &lt;a href="#" class="topPage"&gt;Where we build&lt;/a&gt;
        &lt;a href="#" class="topPage"&gt;Why PMB?&lt;/a&gt;
        &lt;a href="#" class="topPage"&gt;Style&lt;/a&gt;
        &lt;a href="#" class="topPage"&gt;Contact Us&lt;/a&gt;
     &lt;/div&gt;
    &lt;/div&gt;
&lt;/div&gt;

&lt;script src="http://code.jquery.com/jquery-1.8.2.js"&gt;&lt;/script&gt;
&lt;script type="text/javascript"&gt; 

$(function(){
    $(".topPage").click(function(){
        $("#headingBlock").animate({
            'marginTop': "-=140px", "slow"});

});
$("#midPage").click(function(){
     $("#headingBlock").animate({
        'marginTop': "=150px"});
});
});

&lt;/script&gt;

&lt;p&gt;
&lt;/p&gt;


&lt;div id="mainContainer" style="visibility:hidden"&gt;

&lt;div class="mainContent"&gt; 

&lt;p&gt; Lorem Ipsum is simply dummy text of the printing and typesetting industry.&lt;/br&gt; 
Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, &lt;/br&gt;
when an unknown printer took a galley of type and scrambled it to make a type &lt;/br&gt;
specimen book. It has survived not only five centuries, but also the leap into &lt;/br&gt;
electronic typesetting, remaining essentially unchanged. It was popularised in the &lt;/br&gt;
1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more &lt;/br&gt;
recently with desktop publishing software like Aldus PageMaker including versions of &lt;/br&gt;
Lorem Ipsum. &lt;/p&gt;



&lt;p&gt; Lorem Ipsum is simply dummy text of the printing and typesetting industry.&lt;/br&gt; 
Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, &lt;/br&gt;
when an unknown printer took a galley of type and scrambled it to make a type &lt;/br&gt;
specimen book. It has survived not only five centuries, but also the leap into &lt;/br&gt;
electronic typesetting, remaining essentially unchanged. It was popularised in the &lt;/br&gt;
1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more &lt;/br&gt;
recently with desktop publishing software like Aldus PageMaker including versions of &lt;/br&gt;
Lorem Ipsum. &lt;/p&gt;

&lt;/div&gt;
&lt;div id="imgHome"&gt; &lt;img src="design/images/builders.png" alt="Builders"/&gt; 
&lt;/div&gt;
&lt;/div&gt;

&lt;div id="footer"&gt;

&lt;h1&gt; Designed by &lt;a href="http://www.AYLWARD-DESIGN.COM" &gt; Aylward Design &lt;/a&gt; &lt;/h1&gt;

&lt;/div&gt;

&lt;/body&gt;
</code></pre>

<p></p>
