Keep in mind there is third party scripting running on these sites which may be the procurer of the popups you are encountering rather than the uCoz system itself. Additionally if you're clicking on the ad-banner and a popup is appearing this an expected result of such action.
Either way they've been forwarded for our technical division to look into.
Web Applications Developer Been here for 6 years and counting. Visit me at alexmoloney.me.