This is the {{Fmbox}} ([F]ooter and header [m]essage [box]) template.

It can be used to build message boxes for system messages such as MediaWiki:Sp-contributions-footer-anon. It can also be used for footer and header boxes on user pages and for editnotices.

This template works similarly to {{Ambox}} and mostly uses the same parameters. The main differences are that this box is 100% wide and has different colour styles.