If you can't live without the multitasking tabs for your Yahoo Mail, download Mozilla Thunderbird and configure your Yahoo Mail account as an IMAP connection:
http://www.emailquestions.com/mozilla-thunderbird/8246-can-i-use-thunderbird-yahoo-mail.html
*Update! See post #7 to get "tabs" back for your Yahoo Mail - http://www.emailquestions.com/yahoo-mail/8503-get-tabs-back-yahoo-mail.html#post19159
http://www.emailquestions.com/mozilla-thunderbird/8246-can-i-use-thunderbird-yahoo-mail.html
*Update! See post #7 to get "tabs" back for your Yahoo Mail - http://www.emailquestions.com/yahoo-mail/8503-get-tabs-back-yahoo-mail.html#post19159