Usually an extra toolbar is generated by an extension, so you could check the Add-ons page to remove it. Either:

• Ctrl+Shift+a
• "3-bar" menu button (or Tools menu) > Add-ons

In the left column, click Extensions. Then, go hunting!

If you don't see Yahoo named specifically, is there anything else unexpected there?

No version of Firefox for any OS from mozilla.org comes with any toolbars including the Yahoo one.

Either you installed the bundle from Yahoo or some recent software install or update installed the extension into Firefox perhaps.

Where did you download Firefox 29? It is known that some doubtful download sites do have Firefox downloads but all ready with some add ons (like toolbars) installed/activated.
That or you forgot maybe forgot to un-check the Yahoo Toolbar while installing Java?