Blocking spammy websites
Weary of pop-under ads and general junk appearing when you surf the web? Here's a simple approach to tell your computer that requests for that spamware should go nowhere: http://www.mvps.org/winhelp2002/hosts.htm
HOWEVER, a warning: Before you do this, make a backup copy of your Hosts file.
Adding these blocking entries to your Hosts file works with MacOS and Linux, just like it does in Windows; the location of the Hosts file will be different, and you will use a text editor program instead of Notepad.