This problem is in your Yahoo mailbox? Is the problem with advertising messages (the messages are spam) or with advertising from Yahoo? For spam, you can report it to Yahoo; there's no Firefox setting to fix that. For lines of advertising -- i.e., not actual messages -- Yahoo displays one line of advertising above your list of messages. However, it should be only one line... In case this problem is caused by one of your Add-ons, please try disabling ALL nonessential or unrecognized extensions on this page: orange Firefox button (or Tools menu) > Add-ons<br>''in the left column, click:'' Extensions Usually a link will appear above at least one disabled extension to restart Firefox. You can complete your work on the tab and click one of the links as the last step. Any improvement when you return to your email?