There are two main ways that you can contribute.
The best way to report an issue you have come across:
Check if the issue has already been reported. If it has been, please comment on the existing issue.
Check if the issue has already been fixed on the latest
Please try to be as detailed as possible in your report too. What is your environment? What steps will reproduce the issue? What browser(s) and OS experience the problem? What would you expect to be the outcome. All these details will to assess and fix any potential bugs.
First, head over to the Issues tab. Check for any open or closed issues relevant to what you're interested in working on. If your contribution involves a significant amount of work or substantial changes to any part of the project, please open an issue first to check that the work is wanted or matches the goals of the project. For more details, please read: How to properly contribute to open source projects on GitHub.
The best way to get your work merged into the project:
git clone firstname.lastname@example.org:<username>/normalize.css.git).
git remote add upstream git://github.com/necolas/normalize.css.git).
git pull upstream master).
git checkout -b topic-name).
git push origin topic-name).
If you have any other questions about contributing, please feel free to contact me.