The proliferation of all this nastiness has many wondering how to stop it, especially on computers children access. Every few days I get to sift through the misaddressed e-mail pile and route the important ones to their intended owners. So using rules can tag important messages as junk and vice versa. Your e-mail program may also come with a Rules feature, so feel free to use it, but perhaps just send the offending messages to a separate folder, so you can browse them for mistakes.
Web filtering programs work in a similar way.
If a web site's URL or title contains a word deemed inappropriate, you will be denied access to it. They also each have a database of sites deemed appropriate or inappropriate, which is updated occasionally. One of the most famous examples is when the official whitehouse.gov site was blocked because the URL of a biography page on the First Family included the word couple. Just this November, several dozen candidates for U.S. Congress had their sites blocked, including a conservative Republican who changed his position on blocking software after he found out his site was blocked. That one vote apparently wasn't enough, though.