If this has been addressed, I did not find it in a search.
Lately, when I log in to Yahoo’s e-mail, I will type the address in the space provided, then hit tab for the password and the cursor appears in the next field, but sometimes the cursor jumps back to the address field and suddenly I am typing my password into that field, and have to start over.
That often happens if the page has not stopped displaying when you hit the Tab key. When the display is complete, the page refreshes with the cursor in the first box on the page.
Solution is to be patient before hitting Tab and keeping an eye on the cursor.