Many broadband ISPs are now using a "parking page" for bad URLs. When you type a URL that does not resolve to an IP address, rather than get a 404 not found message, the DNS server for the ISP sends you to a specific parking page that serves up adds.
The practice is not new. Verisign got in trouble for it with Sitefinder. MS has something like it in IE. But now it appears that the practice may create security problems.
This also highlights the problem of centralized control by ISPs and allowing ISPs to override user preferences. It creates a gaping security hole, potentially shared by millions of subscribers.
Providers argue that "network neutrality" would prevent them from offering protection to users by impeding the way they manage the network. As this example shows, however, centralized decision making for millions of subscribers has its own problems.