Fixed Positioning
Fixed positioning is a subcategory of absolute positioning. An element
whose position property is set to
fixed always has the viewport as its containing block. For
continuous media, such as a computer screen, a fixed element won’t move
when the document is scrolled. For paged media, a fixed element will be
repeated on every page.
CAUTION: Internet Explorer Compatibility
Fixed positioning isn’t supported by Internet Explorer 6 or prior versions.