Online ads can be harmful to the people that see them. Some sites display banner ads with unpleasant or shocking images that are better left unseen. This is of special concern for children and sensitive people.
Other types of problematic ads include pop-up windows disguised as notifications from social networks, system messages about mandatory “browser updates” or “virus scans.” Clicking on one of these windows could send you to a site where hackers try to get access to your passwords and bank account.
Also commonplace are ads that promise lottery winnings, weight loss, access to databases of personal information, or fortune telling. These ads often link to sites that will attempt to place recurring charges on your mobile phone account.
Some sites simply open new windows containing ads that have nothing to do with the site content. Whether you like it or not, you have to see the ad as you close the window.