I'm not sure what this might be. I'll give you a few different solutions you can try:

Scan for Malware

• Download and Install MalwareBytes Anti-Malware, run a full Scan. http://www.malwarebytes.org/
• Download and Run TDSSKiller http://support.kaspersky.com/faq/?qid=208283363
• Download and Install Microsoft Security Essentials http://windows.microsoft.com/en-US/windows/products/security-essentials (not an official endorsement, but I personally recommend MSE as an awesome permanent anti-virus)
• Double check for all Windows Updates.

Reset Firefox

1. Go to Firefox > Help > Troubleshooting Information.
2. Click the "Reset Firefox" button.
3. Firefox will close and reset. After Firefox is done, it will show a window with the information that is imported. Click Finish.
4. Firefox will open with all factory defaults applied.

The tab is orange and begins with an exclamation point

Did the steps I gave help?

Can you attach a screenshot?

• http://en.wikipedia.org/wiki/Screenshot
• https://support.mozilla.org/kb/how-do-i-create-screenshot-my-problem

Use a compressed image type like PNG or JPG to save the screenshot.

Thank you! Hope you can figure this out. Louise

i belive that is someone trying to chat with you. click the tab and see.

I have no address in my contacts like that. How do I know that this tab is not that of a hacker?

Well, "hackers" won't open up a tab in your email and try to chat with you ;)

But if you don't know who this person is, just click the little "X" and close the tab.

Hope you rec'd the screen shot. Is it possible that this tab is a FIREFOX tab? The color seems right, but I don't trust anyone/anything these days.

That tab is added by the Yahoo mail page.

What do you get when you click that tab?

You can try to clear the Yahoo cookies to see if it has any effect.causing problems:

• Tools > Options > Privacy > Cookies: "Show Cookies"

That will log you out from Yahoo and reset other Yahoo data stored in cookies and not on the server.

You can also try to contact Yahoo to ask them about this tab.

OK. If you are sure that Yahoo has added that tab, I will click on it. I didn't want to infect my computer.

Turns out that the orange tab was a request from someone I do not know to chat with me. I declined. Thanks for your help.

You're welcome.