Besides gaining reputation with your questions and answers, you receive badges for being especially helpful. Badges appear on your profile page, flair, and your posts.

Question Badges

Ask a well-received question on 30 separate days, and maintain a positive question record
252 awarded
Question favorited by 25 users
726 awarded
Question score of 25 or more
2k awarded
Question with 2,500 views
2.7k awarded

Answer Badges

First to answer and accepted with score of 10 or more
5.3k awarded
Edit and answer 50 questions (both actions within 12 hours, answer score > 0)
1 awarded
Provide non-wiki answers of 15 total score in 20 of top 40 tags
70 awarded
Accepted answer and score of 40 or more
327 awarded
Answer score of 25 or more
3.4k awarded
Answer a question more than 60 days later with score of 5 or more
4.3k awarded
Zero score accepted answers: more than 5 and 20% of total
2 awarded

Participation Badges

Vote for a candidate in the final phase of an election
306 awarded
Leave 10 comments with score of 5 or more
357 awarded
Visit the site each day for 30 consecutive days. (Days are counted in UTC.)
2.4k awarded
Earn 200 daily reputation 50 times
3 awarded
Voted 10 times, added 3 posts score > 0, and visited the site on 3 separate days during the private beta
10 posts with score of 2 on meta
46 awarded
Post 10 messages in chat starred by 10 different users
1 awarded
Active member for a year, earning at least 200 reputation
10k awarded

Tag Badges

You must have a total score of 400 in at least 80 non-community wiki answers to achieve this badge.
125 awarded

Moderation Badges

Raise 80 helpful flags
69 awarded
Vote 300 or more times
791 awarded
Complete at least 250 review tasks. This badge is awarded once per review type
76 awarded
Edit 80 posts
55 awarded
Edit 100 posts that were inactive for 6 months
4 awarded
Up vote 100 answers on questions where an answer of yours has a positive score
89 awarded
Edit 50 tag wikis
Create a tag used by 50 questions
171 awarded

Other Badges

Share a link to a question later visited by 300 unique IP addresses
17 awarded
http://mathoverflow.net/help/badges?tab=general&filter=silver
mathoverflow.net
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