Gmail notifier on Google Toolbar 3.0 for Firefox

I just installed the Google Toolbar 3.0 for Firefox.
I saw the new feature, maybe not, which will notify you the incoming Gmail.
When you have some new Gmail, the Gmail icon looks like that in following picture. You can click the triangle right to the Gmail icon, the pulldown menu will show you the title of new emails.
incoming-email

When you click the Gmail icon, and open the Gmail interface, the icon will be changed to normal.
no-incoming-email