Update error screens with the new visual design:

* Bring in new styles for backgrounds/text/link/borders/buttons
* Switch to device-width for the viewport and tweak margins etc so the layout works nicely on all device sizes

Fixes #25956, props johnbillion.



git-svn-id: https://develop.svn.wordpress.org/trunk@26299 602fd350-edb4-49c9-b593-d223f7449a82
Switch to a fluid padding-top on #login so it aligns nicely on small screens. Fixes #26130.

git-svn-id: https://develop.svn.wordpress.org/trunk@26300 602fd350-edb4-49c9-b593-d223f7449a82