You can give upto 10 points of reputation per 24hrs and spread it over upto 10 users. After the 24 hrs are up you get another 10 points.

If you click the scales on one of your posts you can see how many points you have. If you go to the user cp (on the left of the nav bar at the top of the page) you can see who has given you reputation as well.

Oh and if you all give me negative reputation I'll just go into the admin control panel and give myself a shed load more