CSS: fixed to bottom and centered

I need my footer to be fixed to the bottom of the page and to center it. The contents of the footer may change at all time so I can't just center it via margin-left: xxpx; margin-right: xxpx;

The problem is that for some reason this doesn't work:

#whatever {
  position: fixed;
  bottom: 0px;
  margin-right: auto;
  margin-left: auto;
}

I crawled the web and found nothing. I tried making a container div and nada. I tried other combinations and gurnisht. How can I make this happen?

Thanks

You should use a sticky footer solution such as this one :

* {
    margin: 0;
}
html, body {
    height: 100%;
}
.wrapper {
    min-height: 100%;
    height: auto !important;
    height: 100%;
    margin: 0 auto -142px; /* the bottom margin is the negative value of the footer's height */
}
.footer, .push {
    height: 142px; /* .push must be the same height as .footer */
}

There are others like this;

* {margin:0;padding:0;} 

/* must declare 0 margins on everything, also for main layout components use padding, not 
vertical margins (top and bottom) to add spacing, else those margins get added to total height 
and your footer gets pushed down a bit more, creating vertical scroll bars in the browser */

html, body, #wrap {height: 100%;}

body > #wrap {height: auto; min-height: 100%;}

#main {padding-bottom: 150px;}  /* must be same height as the footer */

#footer {position: relative;
    margin-top: -150px; /* negative value of footer height */
    height: 150px;
    clear:both;} 

/* CLEAR FIX*/
.clearfix:after {content: ".";
    display: block;
    height: 0;
    clear: both;
    visibility: hidden;}
.clearfix {display: inline-block;}
/* Hides from IE-mac \*/
* html .clearfix { height: 1%;}
.clearfix {display: block;}

with the html:

<div id="wrap">

    <div id="main" class="clearfix">

    </div>

</div>

<div id="footer">

</div>