CSS Property:
bottom:

Result:
Play with different bottom values for this yellow DIV element.

Note: To "bottom" positioning elements using % (percent) values, use position:absolute.

CSS Code:

div#myBox {
  background-color:yellow;
  width:100px;
  position:absolute;
  bottom:0px;
}
  
Click the property values above to see the result
W3Schools.com - Play it