I've noticed some custom user rules I created in Adblock Plus in Firefox works good in Opera and Maxthon but doesn't work in Internet Explorer 9. Is there a technical reason why filtering IE sometimes doesn't work as good as in other browsers? Take the website http://www.unexplained-mysteries.com/ and use the following rules: unexplained-mysteries.com##DIV[style="height:4px;overflow:hidden"] + DIV[style="height:250px;width:300px;background-color:#000000"] unexplained-mysteries.com##DIV.spacer + DIV[style="height:250px;width:300px;background-color:#000000"] In Opera and Maxthon (using the WebKit engine), it removes the ads and ads placeholders on the right side. However in Internet Explorer (and Maxthon set into the Retro/IE engine) there's two black ad placeholders not removed on the right side. EDIT: Fixed this issue.