Showing posts with label CSS Positioning. Show all posts
Showing posts with label CSS Positioning. Show all posts

Saturday, August 18, 2012

CSS Positioning


Positioning can be tricky sometimes!

Decide which element to display in front!

Elements can overlap!


Positioning

The CSS positioning properties allow you to position an element. It can also place an element behind another, and specify what should happen when an element's content is too big.

Elements can be positioned using the top, bottom, left, and right properties. However, these properties will not work unless the position property is set first. They also work differently depending on the positioning method.

There are four different positioning methods.

Static Positioning

HTML elements are positioned static by default. A static positioned element is always positioned according to the normal flow of the page.

Static positioned elements are not affected by the top, bottom, left, and right properties.

Fixed Positioning

An element with fixed position is positioned relative to the browser window.

It will not move even if the window is scrolled:

Example

p.pos_fixed
{
position:fixed;
top:30px;
right:5px;
}

Try it yourself »

Note: IE7 and IE8 support the fixed value only if a !DOCTYPE is specified.

Fixed positioned elements are removed from the normal flow. The document and other elements behave like the fixed positioned element does not exist.

Fixed positioned elements can overlap other elements.

Relative Positioning

A relative positioned element is positioned relative to its normal position.

Example

h2.pos_left
{
position:relative;
left:-20px;
}
h2.pos_right
{
position:relative;
left:20px;
}

Try it yourself »

The content of relatively positioned elements can be moved and overlap other elements, but the reserved space for the element is still preserved in the normal flow.

Example

h2.pos_top
{
position:relative;
top:-50px;
}

Try it yourself »

Relatively positioned elements are often used as container blocks for absolutely positioned elements.

Absolute Positioning

An absolute position element is positioned relative to the first parent element that has a position other than static. If no such element is found, the containing block is <html>:

Example

h2
{
position:absolute;
left:100px;
top:150px;
}

Try it yourself »

Absolutely positioned elements are removed from the normal flow. The document and other elements behave like the absolutely positioned element does not exist.

Absolutely positioned elements can overlap other elements.

Overlapping Elements

When elements are positioned outside the normal flow, they can overlap other elements.

The z-index property specifies the stack order of an element (which element should be placed in front of, or behind, the others).

An element can have a positive or negative stack order:

Example

img
{
position:absolute;
left:0px;
top:0px;
z-index:-1;
}

Try it yourself »

An element with greater stack order is always in front of an element with a lower stack order.

Note: If two positioned elements overlap, without a z-index specified, the element positioned last in the HTML code will be shown on top.

More Examples

Set the shape of an element
This example demonstrates how to set the shape of an element. The element is clipped into this shape, and displayed.

How to show overflow in an element using scroll
This example demonstrates how to set the overflow property to create a scroll bar when an element's content is too big to fit in a specified area.

How to set the browser to automatically handle overflow
This example demonstrates how to set the browser to automatically handle overflow.

Change the cursor
This example demonstrates how to change the cursor.

All CSS Positioning Properties

The number in the "CSS" column indicates in which CSS version the property is defined (CSS1 or CSS2).

PropertyDescriptionValuesCSS
bottomSets the bottom margin edge for a positioned boxauto
length
%
inherit
2
clipClips an absolutely positioned elementshapeauto
inherit
2
cursorSpecifies the type of cursor to be displayedurlauto
crosshair
default
pointer
move
e-resize
ne-resize
nw-resize
n-resize
se-resize
sw-resize
s-resize
w-resize
text
wait
help
2
leftSets the left margin edge for a positioned boxauto
length
%
inherit
2
overflowSpecifies what happens if content overflows an element's boxauto
hidden
scroll
visible
inherit
2
positionSpecifies the type of positioning for an elementabsolute
fixed
relative
static
inherit
2
rightSets the right margin edge for a positioned boxauto
length
%
inherit
2
topSets the top margin edge for a positioned boxauto
length
%
inherit
2
z-indexSets the stack order of an elementnumberauto
inherit
2