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;
}
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;
}
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;
}
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;
}
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;
}
