Just some quick thoughts, surely yahoo would put up a notice if email was down for service.
Open a command prompt. If in Vista or 7 right click before opening and run as admin.
Can you ping it?
>ping
www.yahoo.comIf you can, your browser or other may have some issue. If not, then:
>ipconfig /flushdns
Try to ping again. If still won't do it, you may have a firewall blocking that port, so don't take that as a 100% indication of a problem. If familiar with your firewall, you can open that port, you'll probably find a label for that tool you can check.
--Check your router to flush the routing table.
Other ideas:
--Download Ccleaner (freeware) and see if that scan finds anything.
--If still no luck, try another browser. IE, Firefox, Opera, Google Chrome...good to have a 2nd on hand anyway. Or, access a proxy site like
www.hidemyass.com and put the url in there to see if that gets it to come up.
--Double check your web security software, make sure yahoo hasn't landed on some kind of blocked website list.