When you make an error in the url for any of my sites an error page comes up that tells you the type of error, with a 404 error being the most common, often resulting from typos. I noticed that I was getting a popup ad when I made a 404 error. This was traced to having an exception for not blocking popups for my domains. I do not recall adding that exception. Also I noticed that there also were several click on spam links of the error page. To make matters worse, my domain name was on the error page which could well have visitors think I put up the popup and clickup spam ads. This likely has been going on a long time, since I usually go directly to the server to do something rather than through a url on the web.
I contacted my server provider, and at first they could not see the ads. Finally, they realized they had ad blockers on the computer they were using to view my sites. They finally found that they were by default adding a link from the error page to a provider of ads. This provider adds an iFrame to the host code that produces the popup and click on ads. Likely the host gets paid a bit for allowing these ad links by default. However, it turns out that you can write your own error pages which will not link to the ad provider as the default pages of the host do. I have thus added custom error pages for 404 errors, which are the main ones you get. I can add custom pages for less common errors in the future if the need arises.
To test for the