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Wix always had and always will have problems. They are slowly trying to understand the importance of SEO for their users. They do a wonderful job giving you a "DIY" site creator which is super easy to use and setup but for that you comprimize a lot of other things. What Dmytro mentioned about funny #! characters in the URLs was actually Wix users nightmare. Around last october (2015) majority of Wix sites got deindexed just because of poor development QA and laziness of Wix programmers. They assumed whatever they want to assume to cut corners with Google Ajax issue. IMO Wix never was good enough SEO wise.