CSS3/FixedPosition

There are a few areas where it's become clear we need to make improvements on the currently specified/implemented behavior of position:fixed:

Mobile and Tablets

The problem of zooming some content and not others.

• Mobile effectively has two viewports: what content layout sees and what the user sees.
• What behavior do we want to support for position: fixed on mobile devices and tablet devices? Goals:
  • Backward compatible with desktop (i.e., leaves most pages usable that weren't designed with zooming in mind)
  • ...
• Links
  • http://www.quirksmode.org/blog/archives/2010/12/the_fifth_posit.html

Patterns like fixed position

Elements you want to scroll up and then stack up against the top of the viewport (or the inverse elements you want to scroll down and stack up against the bottom of the viewport).

• An element that remains in place until it is about to be displaced off the page, and then is fixed position.
  • Example: "show page contents" on http://www.quirksmode.org/blog/archives/2010/12/the_fifth_posit.html
  • Example: Fennec's URL bar when the page is loading