Z-index (layering) Issues
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 stack order number always appears in front of an element with a lower one.
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 in the Preview tab of the creative.
- If you're an agency or advertiser, make sure 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 that ads run on your site are set to a z-index that doesn't conflict.
- How do I troubleshoot this?
Check out these expanding troubleshooters: