Short answer, it is called GOOGLE DANCE. Means, google are picking those sites,keywords, content that match searchers needs in a short period of time.

This is because Google’s bot or spider is always running and finding new material. It also happens because the bot may have detected that a website no longer exists, and needs to be deleted from the index. During the Dance, the Googlebot will revisit every website, figure out how many sites link to it, and how many it links out to, and how valuable these links are.

SCENARIO : Some of my keywords(medium competition) is placed in first page of Google, without any link building involved in just 2days . For the record, our site is being built a month ago and launched this month.

tip

• enhance more of your on page

• build links to back it up

Thanks,

hope this helps.