javascript code:
window.print();
Will tell the browser to start the printing process; it'll usually bring up the print dialogue as if you have pressed CTRL+P. I don't think there's a way to just send a page to the printer without user invention, at least, I hope there isn't. Troll sites would be even more annoying.
You could, for instance, have an image (saying 'print this page!! :C') -
html code:
<img src="http://miffle.com/image.jpg" onClick="window.print();" />
Clicking that would start things. You're correct in saying this is all Javascript.
Regarding not printing the URL on the page, that's browser dependant. I came up against this making invoices for Rowdydow more automated: Chrome currently has no options for configuring the printed URL, page title and page number.
Internet Explorer does, and will remember the settings. Before I had it properly automated with a C# application, I had the Chrome extension to open a page in an IE tab - and printed it from there (it would remember my previous settings and print no URL).
HTH
:)