<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/03/19/horizontally-aligning-tabs-within-a-tabbar-control-in-flex/ -->
<mx:Application name="TabBar_horizontalAlign_test"
        xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white">

    <mx:Style>
        TabBar {
            horizontalAlign: center;
            tabWidth: 100;
            tabHeight: 40;
        }

    </mx:Style>

    <mx:Array id="arr">
        <mx:Object label="Button" />
        <mx:Object label="ButtonBar" />
        <mx:Object label="ColorPicker" />
        <mx:Object label="ComboBox" />
    </mx:Array>

    <mx:Box backgroundColor="haloSilver">
        <mx:TabBar id="tabBar"
                dataProvider="{arr}"
                width="600"
                direction="horizontal" />
    </mx:Box>

</mx:Application>