CSS to centralise a HTML5 div at the bottom of the screen -

i have following html5 document:

<canvas id="mycanvas"> </canvas> <img id="logo" src="/images/logo.png" style="visibility:collapse" /> <div id="adcontrol" style="width: 728px; height: 90px; border: solid 1px red; visibility:visible;"     data-win-control="microsoftnsjs.advertising.adcontrol"     data-win-options="{applicationid: 'xyz', adunitid: '123'}"> </div> 

i'm trying make adcontrol appear in centre @ bottom of screen, beneath canvas. here's css:

#adcontrol {         float:left;       margin: 0px auto;  }  #mycanvas {      float:left;  } 

i've tried various combinations of margin adcontrol, don't seem able centralise it.

do yo mean this?

.box {     width:1024px;     margin: 0px auto; } #adcontrol {        position:fixed;     bottom:0;     width: 728px;      height: 90px;     border: solid 1px red;      visibility:visible; }