If the fixed positioning in CSS only gives the positioning mode position: fixed, the problem caused by the edge displacement is not given - Programmer Sought
CSS: Possible to do position:fixed offset center div? - Stack Overflow
CWLAU's Dev Blog: How to center a HTML Popup dialog with CSS
CSS-only: How can I center fixed width div between two divs that fill the remaining space? - Stack Overflow
CSS3 Archives - Benohead's Software Blog
How to make background image fixed responsive working on actual mobile devices with simple css? - UONG JOWO
How to Center Anything With CSS | Web design, Css, Design shack
Center and crop thumbnails with CSS - Jonathan Nicol