When I blocked m.yahoo, it also blocked yahoo.com. How can I unblock yahoo.com?

I used a link at the bottom of m.yahoo to get my yahoo.com back. Now yahoo.com is blocked from my computer from coming up at all. I get a message the IE cannot display the page and Firefox times out. I cannot find where my firewall has blocked it, so maybe it's something external? I might have used another on to block m.yahoo.com, but it 's been a couple of weeks andI don't remember exactly what transpired,