Rating on website - using cookie?

I've questiones about having a rating feature on the product category on web site. In a real world, how does a site remember the user already entered a rating already? I've thoughts that people may use cookie but that means it needs to store a cookie a someone's browser forever? What if the user deleted all the cookies and cache from the browser?

Do people do it another way?

Thanks.

Ratings are usually stored in cookies, so if the user deletes them, he or she could vote again. Always question yourself this: does this widget have to be absolutely bullet proof? If so, let the user login and registed votes in a database table. If not, store in a cookie (= a more lightweight solution for your website because you can check clientside instead of serverside). Hope this helps.