So you just mean the bookmarks bar.
Browser is Safari, Firefox, whatever name you see in the upper left of the screen, next to the Apple icon.
And to fix that, just go to yahoo.com by tying it into the address bar. Then while there and you have gone to your Email login page, go tot eh Bookmarks menu at the top of the screen and choose Add Bookmark. When the little window open, choose Bookmarks bar (see pic) and then save. It will show up in the bar again.
Now, if that Bar is gone, they don't show there at all, then do this:
Go to the View menu and choose Show Bookmarks Bar.
Your saved bookmark my still be there.
Mine currently says Hide Bookmarks Bar.
Hope this helps. Let me know if you need more.