Source: https://github.com/synthtech/github-mod

Changelog:

2017-03-10
- fix the flash notice fix

2017-03-09
- remove box shadow on focused buttons
- fix flash notice position

2017-03-03
- remove Chrome outlines on focused elements
- remove emoji alignment
- fixed language colour blocks

2017-03-01
- center Octicons within circles
- adjust body spacing due to header height changes
- remove more box shadows
- fix new notification indicator colour

2017-02-28
- fix PR review toolbar shadow

2017-02-21
- adjust flash notice

2017-02-16
- fix floating header breakage
- make PR sidebar sticky again

2017-02-10
- fix flash notice
- fix width of search bar input when using Algolia's extension
- float GitHub Engineering blog header

2017-02-08
- moved Open Sans to an optional setting
- cleaned up some dead code
- realigned emoji

2016-11-10
- fix body padding on developer.github.com
- drop WOFF support
- adjust PR review icons

2016-09-18
- fix z-index of line comment icon

2016-09-14
- fix new user profile navbar

2016-09-13
- adjust pull request toolbar z-index
- remove underline on certain links

2016-09-03
- adjust spacing of repo header nav

2016-09-01
- fix new pull request toolbar

2016-08-07
- fix z-index of sidebar, repo actions, and dashboard context selector
- normalize background colour on organization pages
- adjust backdrop z-index

2016-06-29
- remove unnecessary font subsets
- make floating headers consistent
- remove text-rendering property

2016-05-19
- fix header when logged out

2016-04-19
- fixed new header on some pages
- flatten labels on issues/PRs

2016-04-07
- fix sidebar for the nth time

2016-04-05
- remove temp tooltip fix

2016-04-03
- fix sidebar for the third time
- revert previous changes

2016-03-23
- fix new gist header
- quick fix for gist searchbar

2016-03-19
- fix issue/PR sidebar again

2016-03-15
- float new blog header
- fix reaction tooltips

2016-02-18
- styled help.github.com
- adjusted alignment of octicons
- adjusted the header on developer.github.com

2016-02-15
- flatten disabled buttons and notification indicator
- fix sticky sidebar on issues and PRs
- fix broken header on login pages

2016-01-30
- added Open Sans Semibold

2016-01-29
- updated Open Sans
- removed some more shadows
- fixed font stack

2015-08-24
- fix icon alignment in profile info panel
- fix compatibility with the Octotree extension
- adjust emoji in posts/comments

2015-05-18
- minor visual adjustments

2015-04-03
- flatten more buttons
- added fixed header to developer.github.com

2015-03-27
- fix code formatting bug

2015-03-05
- add WOFF2 support
- fixed header will only apply to the main GitHub site and Gist

2014-10-30
- updated Open Sans
- add Open Sans Italic
- flatten buttons (credit to http://freestyler.ws/style/100106/github-full-flat)

Previously
- changed font to Open Sans
- fixed navbar
- hide "update your info" alert on profile