Buzz tab of Gmail Settings

2) Explanations for why posts get sent to your inbox and an easy-to-find “Mute” link
You'll see a new message at the top of each post in your inbox that explains why it’s there: someone commented on your post, you were @replied, etc. We’ve also added an easy-to-find “mute” link that will stop subsequent comments from bringing the conversation back to your inbox.

Source [ Google Blog ]