I have also seen the phenomenon, ads come and go. Are you logging into the Board with https:// ? Depending on your browser and antivirus (which may also include an ad blocker), may help. When following links from email notifications, sometimes they're http:// and sometimes https:// and I have not been able to see a pattern. But if you always go into the site with https://www.orchidboard.com/community you may get less of them.