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>:
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.
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:
<!DOCTYPE html> <html> <head> <style type="text/css"> img { position:absolute; left:0px; top:0px; z-index:-1; } </style> </head> <body> <h1>This is a heading</h1> <img src="w3css.gif" width="100" height="140" /> <p>Because the image has a z-index of -1, it will be placed behind the text.</p> </body> </html>
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.