adsense banners (iframes) scrolling OVER fixed divs

I have one div with position:fixed 0; that stays on the top of the browser window even when I scroll down. The problem is the adsense banners (iframes) that are out of the fixed div (thus in the main site's content div that should appear under), when I scroll down, 开发者_高级运维they go OVER the fixed div and not below it. I tried to apply a clear: both and z-index to both elements but nothing changed. Can't iframe not go below fixed elements?

thank you

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You need to have proper positioning for z-index to work. Makes sure the iframe container is position:relative or position:absolute