Don't visit their sites or ask for more information. (If you respond to their spams email, you're encouraging them to continue spamming --- they only need a tiny fraction of responses to be profitable.)
There's another reason not to buy anything from a web site that spams: over 95% of spam offers are scams! In fact, not responding to spam is the single most effective way to not get scammed on the web.
Is sending spam illegal ?
Many of the activities associated with the more serious forms of spamming are already illegal . For example, it is a criminal offence to engage in e-mail fraud or to obstruct the use of a computer through spamming. Sending email that contains false or misleading advertising or product claims or that contains pornography is also unlawful. On the other hand, spamming per se is currently legal. To close this gap, the government is proposing to enact an antispam law. The proposed law will balance the interests of businesses seeking to advertise via e-mails legitimately and the interest of e-mail users not to be deluged by unwanted e-mail solicitations. It will also give ISPs, who are the main victims of spam, a right of legal recourse against spammers.
You Can Stop Spams
And with some of the larger service providers, selling accounts to spammer after spammer seemed to be good business to their management. A far better advertising deal for them and their users, than all those bundled post card decks put together. If it were not, a trivial mail filter placed in these service providers' mail gateways would have stopped all that outgoing spam mail long ago. Clearly with them, it is only the volume of our complaints that make a difference.