There are a variety of Internet resources on software applications to filter or block certain types of content from your browser. These can be helpful resources for educators since it is important to be able to keep a watch on the content your students are viewing on the Web. These programs can be configured to block sites by content such as pornography and other potentially offensive topics.
Filters are at best imprecise tools which can generate unpredictable results.
Some work by blocking a pre-selected list of URLs. In some cases, users can add or delete URLs appearing on this list. Other filters block sites based on the presence of certain words. The law of unintended consequences is alive and well here. This approach can let a filter block pornography, but it may also block all references to breast cancer.