Filling sides of a centered div? - css

Question

I want to fill the sides of a centered div with another div or span on each side.
I'm using margining to center the div as shown in this fiddle.
HTML
<div id='A>
<div id='Ad'>
</div>
</div>
CSS
#A{
z-index: 3000;
position: fixed;
width: 100%;
height: 40px;
background: rgba(0,0,0,0.05);
}
/*
div or span to the left
*/
/*
centered div
*/
#Ad{
z-index: 3000;
width: 400px;
height: 40px;
margin-left: auto;
margin-right: auto;
border-left: solid 1px #ff0000;
border-right: solid 1px #ff0000;
}
/*
div or span to the right
*/
How can I have a div that always takes up the remaining space on the left and another div that takes up the remaining space on the right.
Clarification:
Center column needs to be constant width. Left and Right Columns vary with the window size.

Answer 1

This would achieve what you want - it allows you to have a fixed width central div with left and right columns that fill up the remaining space:
HTML:
<div id="A">
<div id="Ad">Centre</div>
<div id="left">Left</div>
<div id="right">Right</div>
</div>
CSS:
#A {
z-index: 3000;
position: fixed;
width: 100%;
height: 400px;
background: rgba(0, 0, 0, 0.05);
}
/*
centered div
*/
#Ad {
z-index: 3000;
width: 400px;
height: 400px;
margin-left: auto;
margin-right: auto;
border-left: solid 1px #ff0000;
border-right: solid 1px #ff0000;
}
#left, #right {
position:absolute;
left:0;
top:0;
right:50%;
margin-right:200px;
background:#F00;
height: 400px;
}
#right {
left:50%;
right:0;
margin-left:200px;
margin-right:0;
}
The key is that the margin on the left/right is half of the central column's total width, so adjust it to take into account any borders or padding.
Working example: http://jsfiddle.net/2AztF/

Answer 2

I would just use 3 <div>s floated within the main container
HTML:
<div id='A'>
<div id='AdLeft'></div>
<div id='Ad'></div>
<div id='AdRight'></div>
</div>
CSS:
#A { overflow:auto }
#AdLeft { float:left; width:25%; }
#Ad { float:left; width:50%; }
#AdRight { float:left; width:25%; }
Here is a modified jsfiddle.

Answer 3

Make 3 divs :
<div id="A"></div>
<div id="B"></div>
<div id="C"></div>
<div style="clear:both"></div>
CSS:
#A,#B,#C{
float:left;
width:10%;
}
#B{
width:80%;
}
Here, B is you main div.
It is good practice to clear when you use float property.

Answer 4

To fill space on the right and left side of your div code use and make sure you have no margin or padding on those sides.
float:right;
float:left;
HTML:
<div class='container'>
<div class='left'></div>
<div class='center'></div>
<div class='right'></div>
</div>
CSS:
.container { overflow: hidden; margin:0; padding:0; }
.right { float: right; width: 150px; }
.center{ float: right; width:50px; margin-right: 50px; }
.left{ float: left; width: 150px; }
The margin-right of .center will fill the space accordingly.