After cloning from remote git repository (at bettercodes) I made some changes, commited and tried to push:
git push origin master
Errors
In case of bettercodes.org, the solution is more poetic - the only problem may be in rights assigned to the project members. Simple members don't have write rights! Please make sure that you have the Moderator or Administrator rights. This needs to be set at bettercodes.org at the project settings by an Administrator, of course.