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Hello Ali & welcome to the Moz community! There could be many factors influencing your SERPs position, especially for a new website. Since your site is new, Google is just learning about its content and performance. It could be that your article came up high in the SERPs and then Google noticed some significant pogo-sticking and lowered its rankings. Have you checked the behavior metrics of the traffic that came through that day? I also suggest adding the term that sent you traffic to Moz's keyword tracking tool so you can monitor its SERPs progress and see how Google is adjusting the rankings.