to put it blankly: It cannot be done (at least i can't imagine a way of ensuring everyone can only vote once in an anonymous vote).

There are several approaches u could try nonetheless:

• IP-Adresses: You can try to remember every IP-Adress that has already voted. But keep in mind, that firewalls masq IP's so that from outside a LAN with some hundred computers looks like one. Another thing are dial-up user which get assigned a new IP whenever they dial up
• Cookies: You can set cookies and try to identify those who already have voted. But as you pointed out yourself people can delete cookies
• Session Management: With SM you can ensure that someone can only vote once per session. But as soon as someone starts a new session he can vote again.

The fact is that to get accurate votes you need an information which is unique and on which the user has no influence. If it's a vote for registered user only you could use something like a user id. Every registerd user has one and he can't change it.

hth
-fen

--
"WHAT CAN THE HARVEST HOPE FOR IF NOT THE CARE OF THE REAPER MAN"
-- Terry Pratchett, "Reaper Man"

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.