CSS layout to place a div on center of the screen

Question

Again about css layout:

#container{
width:979px;
height:590px;
margin-left:auto; //works
margin-right:auto; //works
margin-top:auto; //doesn't work
margin-bottom:auto; //doesn't work
}

So, I want #container to place in the center of screen.
I also tried: margin:auto - without result.

Answer 1

What about something like:

#container{
width:979px;
height:590px;
position:absolute;
left:50%;
top:50%;
margin:-295px 0 0 -490px;
}

Answer 2

Or maybe you can use this solution :

<div class="container">
    <div class="block">
        <p>Hello world, i'm a vertical align div !</p>
    </div>    
</div>

div.bloc { 
    display:inline-block;
    vertical-align:middle;
}