Borders and More with Style Sheets - Alphabetical Property Reference: Bottom (Page 3 of 4 )
bottom IE 5 NN n/a Moz all Saf all Op all CSS 2
The CSS specification calls for this property to define the position of the bottom edge of a positioned elementís margin edge relative to the bottom edge of the next outermost block content container; in the case of positioned elements using the root document as the positioning context, dimensions of the containing block are determined by the browser window of an unscrolled document. In other words, for a top-level positioned element, instead of using the bottom of the document as the comparative edge, these browsers use the bottom of the browser window space (the viewport in CSS terminology). As a result, the precise bottom position of the element varies with the userís browser window size.
When the element is relative-positioned, the offset is based on the bottom edge of the inline location of where the element would normally appear in the content.
bottom: length | percentage | auto
See the discussion about length values at the beginning of this chapter. Negative lengths may be allowed in some contexts, but be sure to test the results on all browsers. You may also specify a percentage value, which is calculated based on the height of the next outermost container. The setting of auto lets the browser determine the bottom offset of the element box on its naturally flowing offset within the containing box.