1. To log in, just make sure that you are logged in at the Yahoo! Mail website. This extension will pick up your browser cookies and check for new mail on its next scheduled checking period. Remember: Do not log out afterwards or else Yahoo! will delete your mail cookies.
2. When there is no new mail, the status-bar icon will disappear. The space will be empty but you can still click on the space to access the options menu.
3. When new mail arrives, a mail icon will appear. Click on it and select "Go to Inbox" to open the Yahoo! Mail website. Or middle-click on the icon to open the Yahoo! Mail website in a new tab.
IMPORTANT: This extension CANNOT check for new mail when you are physically at the Yahoo! Mail website. This is because Yahoo! RESETS the mail counter whenever you visit their mail website. If you want to test this extension, be sure to send yourself an email from another mail account!
Visit my homepage (link below) for more details.
P.S., Remember to middle-click on buttons to open them in a new tab.