I'm having trouble getting `margin:auto` to work, struggling to find a solution

I've been struggling to center the red "countdown" div horizontally, but I haven't had any luck so far. I've spent hours trying to find a solution without success.

http://jsfiddle.net/737tM/

Here is the HTML code:

<div id="container">

  <div id="countdownWrapper">
    <div id="countdown">

    </div>
  </div>

</div>

And here is the CSS code:

body {
margin:0;
background:black;
overflow: hidden;}

#container {
height:100%;
width:100%;
z-index:-900;
position:fixed;
min-width:500px;}

#countdownWrapper {
width:100%;
height:100px;
bottom:0;
position:absolute;
display:block;}

#countdown {
margin-left:auto;
margin-right:auto;
display:block;
width:400px;
height:100px;
background-color: rgba(0, 0, 0, 0.5);
position:absolute;
z-index:1000;
-webkit-border-top-left-radius: 20px;
-webkit-border-top-right-radius: 20px;
-moz-border-radius-topleft: 20px;
-moz-border-radius-topright: 20px;
border-top-left-radius: 20px;
border-top-right-radius: 20px;
background:red;}

Answer №1

It's recommended to eliminate the "position:absolute;" declaration from your countdown component, as margins cannot be accurately calculated on elements with absolute positioning.

Answer №2

Issue resolved! Check out the fix here.

The issue stemmed from the absolute positioning; margins on absolute elements are calculated relative to their own position, not their parent's. Removing the absolute positioning from the countdown div and adjusting the CSS accordingly solved the problem.

#countdown {
    margin: 0 auto;
    display:block;
    ...
}

Answer №3

The issue with your div lies in the

position:absolute;

attribute that you have used on the element called countdown.

If you simply remove this property, your center margining will function correctly.

It is important to note that margins do affect absolutely positioned elements, but they operate differently compared to statically positioned elements.

Understanding how positioning functions is essential. To get started, you can refer to Chris Coyier's informative article here: http://css-tricks.com/absolute-relative-fixed-positioining-how-do-they-differ/.

I hope this explanation is useful for you!

Answer №4

By modifying the code to:

#countdown {
    margin-left:auto;
    margin-right:auto;
    display:block;
    width:400px;
    height:100px;
    background-color: rgba(0, 0, 0, 0.5);
    position:absolute;
    z-index:1000;
    -webkit-border-top-left-radius: 20px;
    -webkit-border-top-right-radius: 20px;
    -moz-border-radius-topleft: 20px;
    -moz-border-radius-topright: 20px;
    border-top-left-radius: 20px;
    border-top-right-radius: 20px;
    background:red;
    top: 0; left: 0; bottom: 0; right: 0;
}

The updated code will effectively center the element on the page. The adjustment is necessary because when using margin: auto, the top and bottom margins default to '0' in the normal flow of content. In this case, with margin-left and margin-right set as 'auto', they are essentially '0'. With position:absolute, the block is taken out of the typical content flow, affecting how the remaining content is rendered. Specifying values for

top:0; left:0; bottom:0; right:0;
creates a new boundary box for the block.

Defining a width and height restricts the block from expanding to fill all available space, prompting the browser to calculate margin:auto based on the newly defined boundaries. Consequently, the margins of the absolutely positioned element align within these constraints. As the block is now positioned absolutely and removed from the regular flow of content, the browser assigns equal values to margin-left and margin-right, ultimately centering the element within the specified bounds.

I trust this explanation clarifies any confusion. Feel free to reach out if you have further questions.

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