Victoria, please take a screenshot of your yahoo e-mail = open yahoo mail, press the key Print Scrn, then open the Paint program, go to Edit menu, choose Paste from there, then go to File menu, choose Save As, choose jpg, give it an easy name (like MailProblem), save it to desktop or My Documents and post it here -- see the attach on the buttom, you'll have to use the Browse button.
If you do that, do not open personal data, because you will present it to us - with the above method you will take a "picture" of your screen. Just be sure that there are no other programs started (like a word document, some important pictures or other documents) on your screen.