Kimmo, this is why I love Mozilla. :) It simply blocks opening of popups when you load or close a page but if a site relies on it (e.g. open a new window for an image) it still works. BTW Opera6 looks good, but I don't think it will get me off Mozilla, it's too much fun. :)...
Another nice software which does this (and it is free for non-commercial use without any limitations) is Link Removed. It also is able to remove ad banners and has a lot of other features.
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-Dominik Dröscher ICQ: 25318265
"Quis custodiet ipsos custodes."