Can't access my WP login pages

I have had this problem before. I have been using 2 wp login pages today for two of my sites. Now, however, when I click on the login link from my bookmarks, I am taken to a dns server bt page on yahoo. I can’t login to any of my 4 wp sites even from the front end, I’m always taken to this dnd server yahoo page. I have cleared cache, cookie, history etc, I am using chrome. I tried firefox, it worked for a while, now no browsers are letting me in. I’m locked out all round. What’s the answer to this one please?