EXCITING STUDY: CSS Horizontal Align

Tuesday, November 22, 2011

CSS Horizontal Align

In CSS, several properties are used to align elements horizontally.

Aligning Block Elements

A block element is an element that takes up the full width available, and has a line break before and after it.
Examples of block elements:

<h1>
<p>
<div>

For aligning text, see the CSS Text chapter.
In this chapter we will show you how to horizontally align block elements for layout purposes.

Center Aligning Using the margin Property

Block elements can be aligned by setting the left and right margins to "auto".
Note: Using margin:auto will not work in IE 8 and earlier, unless a !DOCTYPE is declared.

Setting the left and right margins to auto specifies that they should split the available margin equally. The result is a centered element:

Example

.center
{
margin-left:auto;
margin-right:auto;
width:70%;
background-color:#b0e0e6;
}

Tip: Aligning has no effect if the width is 100%.
Note: In IE 5 there is a margin handling bug for block elements. To make the example above work in IE5, add some extra code

Left and Right Aligning Using the position Property

One method of aligning elements is to use absolute positioning:

Example

.right
{
position:absolute;
right:0px;
width:300px;
background-color:#b0e0e6;
}

Note: Absolute positioned elements are removed from the normal flow, and can overlap elements.

Crossbrowser Compatibility Issues

When aligning elements like this, it is always a good idea to predefine margin and padding for the <body> element. This is to avoid visual differences in different browsers.
There is also another problem with IE when using the position property. If a container element (in our case <div class="container">) has a specified width, and the !DOCTYPE declaration is missing, IE will add a 17px margin on the right side. This seems to be space reserved for a scrollbar. Always set the !DOCTYPE declaration when using the position property:

Example

body
{
margin:0;
padding:0;
}
.container
{
position:relative;
width:100%;
}
.right
{
position:absolute;
right:0px;
width:300px;
background-color:#b0e0e6;
}

Left and Right Aligning Using the float Property

One method of aligning elements is to use the float property:

Example

.right
{
float:right;
width:300px;
background-color:#b0e0e6;
}

Crossbrowser Compatibility Issues

When aligning elements like this, it is always a good idea to predefine margin and padding for the <body> element. This is to avoid visual differences in different browsers.
There is also another problem with IE when using the float property. If the !DOCTYPE declaration is missing, IE will add a 17px margin on the right side. This seems to be space reserved for a scrollbar. Always set the !DOCTYPE declaration when using the float property:

Example

body
{
margin:0;
padding:0;
}
.right
{
float:right;
width:300px;
background-color:#b0e0e6;
}