I'm creating a site where users vote for their favourite music CD or something like that. Users do not register or anything like that to use the site, so I'd like to know of a quick and easy way to prevent the user from voting more than once (within a given time period).

Of course, I know that nothing can ever be 100% accurate -- but I don't want someone just to be able to reload the page 300 times to drastically skew the vote.

My idea was to use some kind of flat file where all the IPs and USER_AGENTs are stored (user agents used to narrow it down a bit among ISPs who proxy all requests), but I'm not sure exactly what the best way is.

Perhaps cookies?

Any help (and especially code!) would be appreciated.

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