A: There are a few possibilities that could lead to some ads not being blocked.
First, check if the filters you subscribed need to be updated. To update, click 'Adblock Plus' >click 'Adblock Plus option'>click 'Update Now".
Second, the website that still shows ads might not be included in the filter you subscribed. Try subscribe more filters or customize your own filter to block the ads. To do this, you need to learn how to write ad filters first. Please refer to this webpage for the filter syntax and guide. https://adblockplus.org/en/filters.
Third, many websites have employed technology for anti-adblock purpose, therefore it is possible that some ads simply can't be blocked.