Z-Index Guidelines

Z-Index Range Content Type Details
< 0 Background Elements
0 - 4,999 Main Content, Standard Ads Standard ad tags in place with regular content. Includes IBA Self Regulation Message (CLEAR Ad Notice)
5,000 - 1,999,999 Expanding Advertising The entire expandable ad unit should be set within this range
2,000,000 - 2,999,999 Floating Advertising Over The Page ads (OTP's)
3,000,000 - 3,999,999 Pop-up Elements Chat windows, message notifications
4,000,000 - 4,999,999 Non-anchored Floating Elements Survey recruitment panels
5,000,000 - 5,999,999 Expanding Site Navigation Elements Drop down navigation, site warnings, etc. Only the expanding portion of navigation elements should be included on this level.
6,000,000+ Full-page Overlays Full-window Over-the-Page (OTP) ads and Between-the-Page ads IF they cover page content
Notes: *Ad designers should consult each publisher individually for their specific Z-index guidelines

Z-index Definition
Enumerated layers of elements and content on a publisher’s webpage. Consideration of the z-element in page content design such as navigation, imagery, and ads is important for providing a seamless experience when page content overlaps (i.e. an expanding ad with a z-index that is lower [on the z-index scale] than navigational elements may give the appearance that page navigational elements are showing through the expanded portions of the ad).

Z-Index Range Use Recommendations
The Z-index represents layers of elements on a webpage. When ad elements and other page elements are layered incorrectly, proper display of either page content or ad content (or both) may be compromised. The accidental “collision” of competing elements on a webpage that share the same Z-index value leads to a poor consumer experience, in the form of distorted or mangled images and text. Accordingly, the establishment of an industry accepted z-index hierarchy and associated numerical range is crucial to solving the occurrence of collisions. Please note that adoption of these new Z-index guidelines by all publishers will take time. Creative designers are advised to consult directly with publishers for their individual Z-index guidelines.