怎么让一个div里面的多个div在不同分辨率下都处于居中 在线求 急

具体代码如下：
<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" runat="Server">
<asp:ScriptManager ID="sm" runat="server">
</asp:ScriptManager>
<div id="div_News_list_imageTitle" class="div_News_list_imageTitle"></div>
<div class="div_News_list" id="div_News_list">
<div id="div_News_list_ Navie" class="div_News_list_Navie"></div>
<div id="div_News_list_Content" class="div_News_list_ol" style="text-align: center;">
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
<div id="div_News_list_Content_DiningRoomBody" class="div_News_list_Content_DiningRoomBody" runat="server">
<ul align="center">
<asp:DataList RepeatColumns="3" ID="DataList1" runat="server" RepeatDirection="Horizontal">
<ItemTemplate>
<li class="listbox div_News_list_Content_Custom_liimage">
<div class="listimg">
<div class="summary">
<div class="summarytxtt" style="text-align: center;"></div>
</div>
</div>
</li>
</ItemTemplate>
</asp:DataList>
</ul>
</div>
<div style="margin-bottom: 10px; width: auto; float: right;">
</div>
</ContentTemplate>
</asp:UpdatePanel>
</div>
<div id="div_News_list_Return" class="div_News_list_Return">
<input type='button' onclick='goBack()' value='返回' />
</div>
</div>