How do you get rid of advertisements popping up on your notification bar?

That's normally caused by some app you may have downloaded recently. Have you downloaded any apps that might be connected to the pop-up in any way? If so just uninstalling the app should do it.

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Android News I Android Apps I > App Center

I got the same problem, but I have downloaded lots of apps, and the ads just started randomly some time after.

Is there any way of finding out witch app causes theese ads?

any ads appearing on your notification bar should have basic details on how to opt out, unless you've 'voluntarily' let your number be used for marketing.

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Sinkster