If you're looking for literary agents to submit to, this site will probably help you out... http://www.agentsleuth.com It lists hundreds of agents, what they represent, their submission guidelines and their query email addresses.
Similar sites with more searchable formats at querytracker.net and agentquery.com. Last I checked, both of these sites did at least some vetting of the agents they listed, which is important in order to avoid scams. I don't know if the list from the OP does this. And make sure that you check out any agents at WritersBeware, Preditors and Editors and AW before you get too far into the process. - @Sack-a-Doo! I'd guess that means no generic queries, but I don't know for sure...
No 'dear agent' means queries should be addressed to the agent by name. A lot of people send a mass query, copying in 50 agents...
Ah! Okay. I thought it was playing off the "Dead Dear John" cliché; it was confusing. EDIT: A "Dead John" letter would be even worse.