Hi there. Have you tried to contact Yahoo e-mail support? It seems that's more likely a problem with the way the website is serving content to Firefox since what you're describing is a website functionality.

Unfortunately I don't use Yahoo e-mail myself, but someone else might be able to provide more specific help. So, my recommendation would still be to contact Yahoo about this, and provide a screenshot of what you're seeing (and expecting to see).

Good luck!

My same email account works fine with Internet Explorer with (windows 7) and with Firefox version 9 on a different PC with (vista). I did call my internet provider and they suggested to uninstall and re-install Firefox which I did but that didn't help. They also had me delete history and cookies. I would think that if the same email works with IE, it should work same with Firefox. I may have to use IE until this issue gets resolved. Thanks for your feedback.