1.
position:static
The default positioning for all elements is position:static, which means the element is not positioned and occurs where it normally would in the document. Normally you wouldn't specify this unless you needed to override a positioning that had been previously set.
#div-1 {
position:static;
}
2.
position:relative
If you specify position:relative, then you can use top or bottom, and left or right to move the element relative to where it would normally occur in the document.Let's move div-1 down 20 pixels, and to the left 40 pixels:
#div-1 {
position:relative;
top:20px;
left:-40px;
}
Notice the space where div-1 normally would have been
if we had not moved it: now it is an empty space. The next element (div-after)
did not move when we moved div-1. That's because div-1 still occupies that
original space in the document, even though we have moved it.
3. position:absolute
When you specify position:absolute, the element is
removed from the document and placed exactly where you tell it to go.
Let's move div-1a to the top right of the page:
#div-1a {
position:absolute;
top:0;
right:0;
width:200px;
}
Notice that this time, since div-1a was removed from the document, the other elements on the page were positioned differently: div-1b, div-1c, and div-after moved up since div-1a was no longer there.
Also notice that div-1a was positioned in the top right corner of the page. It's nice to be able to position things directly the page, but it's of limited value.
What I really want is to position div-1a relative to div-1. And that's where relative position comes back into play.
Footnotes
· There is a bug in the Windows IE browser: if you specify a relative width (like "width:50%") then the width will be based on the parent element instead of on the positioning element.
4.
position:relative + position:absolute
If we set relative positioning on div-1, any elements within div-1 will be positioned relative to div-1. Then if we set absolute positioning on div-1a, we can move it to the top right of div-1:
#div-1 {
position:relative;
}
#div-1a {
position:absolute;
top:0;
right:0;
width:200px;
}
5. two column absolute
Now we can make a two-column layout using relative and
absolute positioning!
#div-1 {
position:relative;
}
#div-1a {
position:absolute;
top:0;
right:0;
width:200px;
}
#div-1b {
position:absolute;
top:0;
left:0;
width:200px;
}
6. two column absolute height
One solution is to set a fixed height on the elements.
But that is not a viable solution for most designs,
because we usually do not know how much text will be in the elements, or the
exact font sizes that will be used.
#div-1 {
position:relative;
height:250px;
}
#div-1a {
position:absolute;
top:0;
right:0;
width:200px;
}
#div-1b {
position:absolute;
top:0;
left:0;
width:200px;
}
7. float
For variable height columns, absolute positioning does not
work, so let's come up with another solution.
We can "float" an element to push it as far
as possible to the right or to the left, and allow text to wrap around it. This
is typically used for images, but we will use it for more complex layout tasks
(because it's the only tool we have).
#div-1a {
float:left;
width:200px;
}
8. float columns
If we float one
column to the left, then also float the second column to the left, they will
push up against each other.
#div-1a {
float:left;
width:150px;
}
#div-1b {
float:left;
width:150px;
}
9. float
columns with clear
Then after the floating elements we can "clear" the
floats to push down the rest of the content.
#div-1a {
float:left;
width:190px;
}
#div-1b {
float:left;
width:190px;
}
#div-1c {
clear:both;
}
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