Display The Whole Page In The Center Of The Browser?

i have three divs outside my contentplaceholder masterpage code:

<div id="content-outer" class="clear">
<div id="content-wrapper">
<div id="content">
<asp:ContentPlaceHolder ID = "ContentPlaceHolder1" runat="server" >
</asp:ContentPlaceHolder>
</div>
</div>
</div>

the width of content outer div is 1400px,it works well in the screen whose width is 1400 or more but when i run it in the scree of width 1024, the whole page starts from left,,,i want to center align my page when open in the browser,i have given some css properties like

content-outer:
margin-left:auto;
margin-right:auto;(not working)

but i m not able to center align my whole page,,,plz tell me how can i do that,,i have also given the same properties for body but again no luck