I noticed that some websites such as polldaddy<http://polldaddy.com/account/home.php> has fascinating poll service. And I am just curious about how it prevents user from polling the same poll for more than once. Or more accurately, I am a dynamic IP user. And I found that if I have polled once for a certain poll and after some time, I changed my IP when I got connected to the Internet again, I cannot poll the previous one for the second time. So I am confused how polldaddy <http://polldaddy.com/account/home.php> can figure out that I have polled even if I had changed my IP. Is there any way to achieve that? Thanks in advance.
