What is the highest possible Z-Index Value?
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Skip to my recommended highest Z Index Value

Backstory:
In January of 2010, shortly after I took up a consulting gig at Reuters, I noticed a disturbing pattern: 4 times in a single month, we had to take down an ad from the site because it was overlaying other elements on the page – most frequently affecting the main site navigation drop down – creating a really bad user experience. (At the time, Reuters had just relaunched with this new site a month ago – thus why the bug wasn’t diagnosed/fixed yet). Advertisers were setting the z-index of their ads at a higher number than our own key page elements – most frequency the main site navigation.
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