I would say the most likely scenario is that you are/were using some kind of public WIFI and the owner was either attempting something malicious or was directing you to some kind of site for you to agree to tOs of using their WIFI and/or to pay for using their WIFI
I'm not using wifi bro. Last time I use wifi was last year. I only use data connection.
Just change your DNS settings and you should be fine. I had to switch from openDNS a while back as well. You might want to look at OpenNIC[1] or just use the your ISPs DNS. Im pretty happy with OpenNIC.
[1] http://wiki.opennicproject.org/HomePage