Make it a topic of conversation often. I have blocked my computer from being able to access to porn sites but every now and then pornographic advertising will appear on a non porn site. You might also want to contact the sites where this advertising comes up. They might not be aware of it. Cookies are identifying codes placed on your computer that are used to track what Web sites you visit and what you do at Web sites.
Cookies allow companies to create individual profiles on people who visit their sites.
Cookies also can be used to create tailor-made advertising messages directed to you or your children. To avoid having cookies track you through Web sites, you can open up the options setting in your Web browser and change it so that a Web site will have to get your permission to place a cookie on your computer. Not that they're cure alls but surely a first step. Part of what makes this issue so difficult for parents is that children tend to learn their ways around new technologies faster than their parents. Sometimes it can seem like a mystery to parents.