I am no longer maintaining the Mail Checker Minus extension. I recommend switching over to Jason Savard's Checker Plus For Gmail. He's already done a good bit of work cleaning up code and adding new features. For those of you happy with the extension as is, I will continue to make it available via the Chrome Web Store, but please note that I will not be fixing bugs or supporting the extension.
It's fairly likely that you found this site because of the Google Chrome Extension I now maintain, Mail Checker Minus. That's a pretty good assumption since it's fairly popular and links here. For the two people who somehow found my site and don't know about Mail Checker Minus, it is (in my opinion) one of the most useful plugins for Chrome. It allows you to see the number of unread mails for Gmail at a glance, preview them, and even take actions on them.