Wow, this problem is popular. It's based on a misunderstanding in the vertical-align
property. This excellent article explains it:
Understanding vertical-align
, or "How (Not) To Vertically Center Content" by Gavin Kistner.
“How to center in CSS” is a great web tool which helps to find the necessary CSS centering attributes for different situations.
In a nutshell (and to prevent link rot):
- Inline elements (and only inline elements) can be vertically aligned in their context via
vertical-align: middle
. However, the “context” isn’t the whole parent container height, it’s the height of the text line they’re in. jsfiddle example
- For block elements, vertical alignment is harder and strongly depends on the specific situation:
- If the inner element can have a fixed height, you can make its position
absolute
and specify its height
, margin-top
and top
position. jsfiddle example
- If the centered element consists of a single line and its parent height is fixed you can simply set the container’s
line-height
to fill its height. This method is quite versatile in my experience. jsfiddle example
- … there are more such special cases.
2015 update: the flexbox approach
There are two other answers briefly mentioning flexbox; however, that was more than two years ago, and they don't provide any examples. The specification for flexbox has definitely settled now.
Note: Though CSS Flexible Boxes Layout specification is at the Candidate Recommendation stage, not all browsers have implemented it. WebKit implementation must be prefixed with -webkit-; Internet Explorer implements an old version of the spec, prefixed with -ms-; Opera 12.10 implements the latest version of the spec, unprefixed. See the compatibility table on each property for an up-to-date compatibility status.
(taken from https://developer.mozilla.org/en-US/docs/Web/Guide/CSS/Flexible_boxes)
All major browsers and IE11+ support Flexbox. For IE 10 or older, you can use the FlexieJS shim.
To check current support you can also see here:
http://caniuse.com/#feat=flexbox
Working example
With flexbox you can easily switch between any of your rows or columns either having fixed dimensions, content-sized dimensions or remaining-space dimensions. In my example I have set the header to snap to its content (as per the OPs question), I've added a footer to show how to add a fixed-height region and then set the content area to fill up the remaining space.
html,
body {
height: 100%;
margin: 0;
}
.box {
display: flex;
flex-flow: column;
height: 100%;
}
.box .row {
border: 1px dotted grey;
}
.box .row.header {
flex: 0 1 auto;
/* The above is shorthand for:
flex-grow: 0,
flex-shrink: 1,
flex-basis: auto
*/
}
.box .row.content {
flex: 1 1 auto;
}
.box .row.footer {
flex: 0 1 40px;
}
<!-- Obviously, you could use HTML5 tags like `header`, `footer` and `section` -->
<div class="box">
<div class="row header">
<p><b>header</b>
<br />
<br />(sized to content)</p>
</div>
<div class="row content">
<p>
<b>content</b>
(fills remaining space)
</p>
</div>
<div class="row footer">
<p><b>footer</b> (fixed height)</p>
</div>
</div>
In the CSS above, the flex property shorthands the flex-grow, flex-shrink, and flex-basis properties to establish the flexibility of the flex items. Mozilla has a good introduction to the flexible boxes model.
Best Answer
This is a pure CSS2 solution for horizontally and vertically centering without known sizes of either container nor child. No hacks are involved. I discovered it for this answer and I also demonstrated it in this answer.
The solution is based on
vertical-align: middle
in conjunction withline-height: 0
, which parent has a fixed line-height.The HTML:
And the CSS:
Tested on Win7 in IE8, IE9, Opera 11.51, Safari 5.0.5, FF 6.0, Chrome 13.0.
The only caveat is IE7, for which the two innermost elements have to declared at one line, as demonstrated in this fiddle:
Note that the span's are also required for IE7. In every other browser, the span's may be div's.