BleepingComputer.com: IE 8-9 and problems with Add-ons

Every time I reformat the PC run the correct procedures. But whether I use IE 8 or 9 some site always tells me "unable to perform an add-ons for this site." Or add-ons or there, but there is conflicting with the site. Because from what I see a banner always appears empty, white or an image file or an html file. But at the same site there are other banners identical, with the same extension, but they are displayed correctly. It 'my problem or a problem of the sites? Thank you.