center div between 2 divs

hello
i have 3 divs in a container. i seem to be having trouble getting the middle one (mailcenter) to center between the 2. i have attached my code and would be grateful if someone could tell me where i am going wrong. many thanks

css
==================================
#mailleft	{
	float: left;
	width: 150px;
	margin-top:180px;
	margin-left:17px;

	}
#mailright	{
	
float: right;
width: 150px;
margin-top:180px;

	
	}
.mailcenter	{

float: left;
width: 70%;
margin-top:180px;
 
	}
#container{
margin: 0 auto;   
text-align: left; 
width:97%;
		
		}

html
===============================================

<div id="container">
<div id="mailleft">
	<div id="accordion3">
    	<h2><a href="#">Mail</a></h2>
    	<div>First content</div>
    </div></div>
	<div class="mailcenter">
			<div id="accordion">
    		<h2><a href="#"><?php echo $_SESSION['kt_name_usr']; ?></a></h2>
    	<div>First content</div>
    </div></div>
	<div id="mailright"><div id="accordion2">
    	<h2><a href="#">Utilities</a></h2>
    	<div>First content</div>
    	<h2><a href="#">Tools</a></h2>
    	<div>Second content</div>
	</div></div>
</div>

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