Three DIVs of which two have a dynamic width - css

Question

What I am trying to is have a header image centered on the top with a different color background on either side, dynamically filling the rest of the page. The structure would look like this:
<div id="Header_Container">
<div id="Header_Left"></div>
<div id="Header_Center"></div>
<div id="Header_Right"></div>
</div>
The Header_Center is of 960px and the Header_Left and Header_Right should fill either side of the image to the edge of the page and change width as the page width changes.
I can not get the CSS to work properly.

Answer 1

I assume you want those 3 divs to fill each with different content, the outsides filled fluidly or multiline. Otherwise the answer could be much 1) more simple. I also assume that the center div defines the total height of the header.
Given these two assupmtions, still a few different scenarios are thinkable of which I will give 4 examples from which you can choose the best fitting solution.
The HTML is exactly yours.
The CSS looks like:
#Header_Container {
width: 100%;
position: relative;
}
#Header_Left {
position: absolute;
left: 0;
right: 50%;
margin-right: 480px;
}
#Header_Right {
position: absolute;
left: 50%;
right: 0;
margin-left: 480px;
top: 0;
}
#Header_Center {
width: 960px;
position: relative;
left: 50%;
margin-left: -480px;
}
Now, you could change behaviour of left and right with a few extra styles:
height: 100%;
overflow: hidden;
See demonstration fiddle.
1) When the sides may be partially invisible outside the browser window (in case which you would align content in de left div to the right, and vise versa), then I suggest the solution in this fiddle demo which does not require absolute positioning at all so that any content below the header is properly cleared in all circumstances.

Answer 2

You must fix it using padding and box model + position : relative - it can be done without HTML Change
<div id="Header_Container">
<div id="Header_Left"></div>
<div id="Header_Right"></div>
<div id="Header_Center"></div>
</div>
And CSS ( 100px is for example )
#Header_Container{ overflow: hidden; height: 100px; }
#Header_Container *{ box-sizing: border-box; height: 100%; }
#Header_Left{ width: 50%; padding-right: 480px; }
#Header_Right{ margin-left: 50%; width: 50%; padding-left: 480px; position: relative; top: -100% };
#Header_Center{ margin: 0 auto; width: 960px; position: relative; top: -200%; }
Example is here http://jsfiddle.net/ZAALB/2/
EDITed incorrect example

Answer 3

If I got you right then this might be a possible solution.
​#container {
width: 100%;
height: 150px;
}
#left {
position: absolute;
left: 0;
width: 50%;
height: 150px;
background-color: #FF0000;
}
#right {
position: absolute;
right: 0;
width: 50%;
height: 150px;
background-color: #0000FF;
}
#center {
position: absolute;
left: 50%;
margin-left: -480px;
width: 960px;
height: 150px;
background-color: #888888;
}
​
#left basically says that the element will be positioned absolute and attached to the left side with a width of 50%. Same applies to #right just for the right side.
#center positions the element absolute pushed 50% to the left and then with a negative margin of width/2 which in your case would be 480px to position it in the center.
The order of the elements in the HTML is important for this hack.
<div id="container">
<div id="left"></div>
<div id="right"></div>
<div id="center"></div>
</div>​
The #center DIV must be the last element if you don't want to work with z-indexes.
Here's a fiddle to test it.

Answer 4

HTML:
<div id="Header_Container">
<div class="Header_Side" id="Header_Left"></div>
<div class="Header_Side" id="Header_Right"></div>
<div id="Header_Center"></div>
</div>
CSS:
#Header_Container {
position: relative;
width: 100%;
}
#Header_Container > div {
height: 158px; /* height of the image */
}
.Header_Side {
position: absolute;
width: 50%;
}
#Header_Left {
left: 0;
background-color: blue;
}
#Header_Right {
left: 50%;
background-color: green;
}
#Header_Center {
position: relative;
width: 158px; /* width of the image */
margin: 0 auto;
background-image: url('...');
}
Also see this example.

Answer 5

This works, but you need to change your HTML: http://jsfiddle.net/gG7r7/1/
HTML
<div id="header_background_container">
<div id="header_left"></div>
<div id="header_right"></div>
</div>
<div id="header_content_container">
<div id="header_content"><p>Content goes here</p></div>
</div>
CSS
#header_content_container {
position:absolute;
z-index:1;
width: 100%;
height: 100%;
}
#header_content {
width: 960px;
margin: 0 auto;
background: red;
height: 100%;
}
#header_left {
background: white;
width: 50%;
height: 100%;
position: absolute;
z-index: 0;
}
#header_right {
background: black;
width: 50%;
height: 100%;
position: absolute;
z-index: 0;
}