Over the years, Google has flip-flopped on their stance on display:none, hiding content on your web page based on user interface purposes, but at the same time, offering the content based on how you use the navigation.
Back in 2007 Google said it was okay to use, that it won't necessarily kick you out of their index. Google has said time and time again, there are valid design reasons to use the display:none CSS.
But as we know from the hidden content discussion, Google said most recently they discount the content that is hidden.
Now, Gary Illyes from Google responded to a StackOverflow thread saying using display:none can back fire, that Google weighs the content in the display less.
Gary wrote:
Most of the major search engines (including Google) are rendering the content they receive from the website, in our (Google's) case with something close to a headless browser, so whatever you do for the users the search engines will also get it. Serving different stuff to search engines however will get you into a dangerous area, named cloaking.Hiding the content with a display:none might backfire on you. We are giving hidden content way less weight in ranking.
This is not really new, webmasters have said even though Google says this, they don't believe it. But Google has said in the past year several times that content that is hidden is given less weight in rankings.
Forum discussion at StackOverflow.
