SO jQuery animate widths with CSS

Animate widths with Javascript and CSS transitions

HTML

<link rel="stylesheet" href="http://twitter.github.com/bootstrap/assets/css/bootstrap.css">
<script src="http://twitter.github.com/bootstrap/assets/js/bootstrap.js"></script>
<div class="container openLeft">

    <div class="row">
        <div class="span12">
            <p class="closeLeft"><button class="btn btn-large" type="button" id="closeTrigger">Close    'Em</button></p>
            <p class="openLeft"><button class="btn btn-large" type="button" id="openTrigger">Open 'Em</button></p>

        </div>
    </div>
    <div class="row">
       <div class="span9 to-enlarge">right</div>       
    </div>
</div>

CSS

.container{
    overflow:hidden;
    color:black;
}

.to-hide {
    background-color: #999;  
}
.to-enlarge {
    background-color: #ccc;
}

/* ------------------- */
/* show / hide buttons */
/* ------------------- */

.container.closeLeft p.closeLeft{
    display:none;}
.container.openLeft p.openLeft{
    display:none;}


/* -----------------*/
/*  Close Left       */
/* -----------------*/

.closeLeft .span3{
    opacity:0;
    filter:alpha(opacity=0); /* For IE8 and earlier */  
    margin-left:-200px;
    width:0;
    overflow:hidden;
}

.closeLeft .span9{
    width:940px;
   
}

/* -----------------*/
/*  Open Left       */
/* -----------------*/

.openLeft .span9{
    width:700px;   
}

/* -----------------*/


/* -----------------*/
/* CSS Transitions */
/* -----------------*/

.span3{
    transition: all 2.5s;
-moz-transition:all 2.5s; /* Firefox 4 */; 
-webkit-transition: all 2.5s; /* Safari and Chrome */
-o-transition: all 2.5s; /* Opera */
}

.span9{
   transition: all 2s;
-moz-transition:all 2s; /* Firefox 4 */; 
-webkit-transition: all 2s; /* Safari and Chrome */
-o-transition: all 2s; /* Opera */
}

JavaScript

$("#closeTrigger").click(function() {
    
$('.container').removeClass('openLeft').addClass('closeLeft');  
    });

$("#openTrigger").click(function() {
    $('.container').removeClass('closeLeft').addClass('openLeft');  
    });