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Z-index (layering) Issues

  • Explanation
    Z-index errors are often at the root of layering issues. The z-index property specifies the stack order of a creative element. An element with a higher stacking-order number always appears in front of an element with a lower one.

  • Symptoms
    The ad might expand under content with a higher z-index. Or other site content (such as the site navigation bar) might be set to a lower z-index than the ad and therefore expand under the banner or expanding ad, as shown in the image.
  • How do I know if this is my issue?
    Use a browser’s developer tool, such as Firebug for Firefox, to check the z-index of the ad and the other elements on the page that may be triggering the issue. The developer tool lets you test your changes to the ad's z-index before you make changes in DFP or DCM Trafficking.
  • How can I avoid this?
    The z-index value of a DoubleClick Rich Media ad is set to 1000000 by default.
    DFP publishers can change the z-index value on the Preview tab of the creative.
    • If you're an agency or advertiser, make sure that you build the ad to conform to z-index site requirements, which are often imposed to prevent such issues. And, if needed, you can find and change the z-index field in the Assets tab of the creative in DCM Trafficking.
    • If you're a publisher and you allow expandable ads on your site, take note of the z-index of your site content (such as the navigation bar) and require ads running on your site to be set to a z-index that doesn't conflict.

  • How do I troubleshoot this?
    Take a look at these expanding troubleshooters:
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