Centering lines of Text, Block or Image

Centering elements in a web page is probably one of the most common tasks for CSS.
There are three kinds of centering:
- Centering lines of text.
- Centering a block of text or an image.
- Centering a block or an image vertically.

Centering lines of text

To center lines of text horizontally in a paragraph, in a heading, a DIV or other HTML element, CSS has the text-align property, to which apply the value: center.
- Example:

<style>
h3 {
 border: 1px solid blue;
 text-align: center;
}
#idiv {
 border: 1px dashed green;
 text-align: center;
}
</style>

<h4>Example center text</h4>

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<div id='idiv'>Div with text centered.</div>

Centering a block or an image

To center a block as a whole (the left and right margin to be equal), you must set the left and right margins to auto, and specify a width for that block.
- Example:

<style>
#idiv {
 margin-left: auto;
 margin-right: auto;
 width: 200px;
 border: 2px dashed blue;
 padding: 5px;
}
</style>

<h4>Example </h4>
<div id='idiv'>Div centered. The lines inside the block are not centered (they are left-aligned).</div>

• In the same way you can center an image: make it into block of its own (with display:block; property) and apply the margin properties to it. For example:

<style>
#idimg {
 display: block;
 margin-left: auto;
 margin-right: auto;
 border: none;
}
</style>

<h4>Example center image</h4>

<div>
 Some text or other content...
 <img src='css/css3.jpg' alt='Text for image' width='200' height='100' id='idimg' />
</div>

Centering Vertically

To center blocks vertically, you must add them inside another block that has a certain 'height', and set vertical-align: middle;, then the trick is to specify that this parent block is formatted as a table cell (with display: table-cell;), because the contents of a table cell can be centered vertically.

- The example below centers a paragraph inside a <div>.

<style>
div.container {
 height: 200px;
 border: 3px dotted blue;
 display: table-cell; /* forms as a table cell */
 vertical-align: middle;
 padding: 3px 4px;
}
</style>

<h4>Example center paragraph vertically</h4>

<div class='container'>
 <p>
 This paragraph is vertically centered.<br>
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 </p>
</div>

• In the same way you can center text and image vertically. The following example centers an image and a line of text vertically and horizontally, inside a DIV.

<style>
div.container {
 height: 250px;
 border: 3px dotted blue;
 display: table-cell; /* forms as a table cell */
 vertical-align: middle; /* center vertically */
 text-align: center; /* center horizontally */
 padding: 3px 4px;
}
</style>

<h4>Example center image vertically</h4>

<div class='container'>
 <img src='css/css3.jpg' alt='Text for image' width='170' height='100' /><br>
 This line of text and the image above are vertically and horizontally centered.
</div>

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Daily Test with Code Example

HTML

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Which tag is used in <table> to create table header cell?

<table><tr>
  <th>Title 1</th>
  <th>Title 2</th>
</tr></table>

Which CSS property sets the distance between lines?

line-height word-spacing margin

.some_class {
  line-height: 150%;
}

Which function opens a new browser window.

alert() confirm() open()

document.getElementById("id_button").onclick = function(){
  window.open("http://coursesweb.net/");
}

Indicate the PHP function that returns an array with names of the files and folders inside a directory.

mkdir() scandir() readdir()

$ar_dir = scandir("dir_name");
var_export($ar_dir);

Centering lines of Text, Block or Image

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