Las cookies no son ilimitadas .. tienen sus restricciones de cuantos datos puedes almacenar en ella:
Aquí tienes las especificaciones:
http://wp.netscape.com/newsref/std/cookie_spec.html Cita: There are limitations on the number of cookies that a client can store at any one time. This is a specification of the minimum number of cookies that a client should be prepared to receive and store.
300 total cookies
4 kilobytes per cookie, where the name and the OPAQUE_STRING combine to form the 4 kilobyte limit.
20 cookies per server or domain. (note that completely specified hosts and domains are treated as separate entities and have a 20 cookie limitation for each, not combined)
Servers should not expect clients to be able to exceed these limits. When the 300 cookie limit or the 20 cookie per server limit is exceeded, clients should delete the least recently used cookie. When a cookie larger than 4 kilobytes is encountered the cookie should be trimmed to fit, but the name should remain intact as long as it is less than 4 kilobytes.
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No sé si usas algún sistema de usuarios para esas votaciones .. o el voto es libre (cualquiera que ingrese a tu página puede votar) .. Pero, sería ideal que gestionases usuarios, así puedes llevar mejor el control de quien vota y cuanto.
Un saludo,