bottom

The bottom CSS property participates in specifying the position of positioned elements.

For absolutely positioned elements, that is those with position: absolute or position: fixed, it specifies the distance between the bottom margin edge of the element and the bottom edge of its containing block.

For relatively positioned elements, that is those with position: relative, it specifies the distance the element is moved above its normal position.

However, the top property overrides the bottom property, so if top is not auto, the computed value of bottom is the negative of the computed value of top.

Values

<length> Is a negative, null or positive that represents:
for absolutely positioned elements, the distance to the bottom edge of the containing block; for relatively positioned elements, the offset that the element is moved above its position in the normal flow if it wasn’t positioned.
<percentage> Is a of the containing block’s height, used as described in the summary.
auto Is a keyword that represents: for absolutely positioned elements, the position the element based on the top property and treat height: auto as a height based on the content. for relatively positioned elements, the offset the element from its original position based on the top property, or if top is also auto, do not offset it at all.
inherit Is a keyword indicating that the value is the same than the computed value from its parent element (which may not be its containing block). This computed value is then handled like it was a , or the auto keyword.

Example

<!DOCTYPE html>
<html>
        <head>
        <title>Position at bottom, absolute or fixed</title>
        <style type="text/css">
p {
	font-size: 30px;
	line-height: 3em;
}
div.pos {
	width: 49%;
	text-align: center;
	border: 2px solid #00f;
}
div#abs {
	position: absolute;
	bottom: 0;
	left: 0;
}
div#fix {
	position: fixed;
	bottom: 0;
	right: 0;
}
</style>
        </head>
        <body>
<p> This <br>
          is <br>
          some <br>
          tall, <br>
          tall, <br>
          tall, <br>
          tall, <br>
          tall <br>
          content. </p>
<div id="fix" class="pos">
          <p> Fixed </p>
        </div>
<div id="abs" class="pos">
          <p> Absolute </p>
        </div>
</body>
</html>