Why is keyword ranking difference between day and night?
 

Have always wondered why my site at night in the second, the day the top ten can not find it? Why is this?

It call google dance, we use this term when google busy to re-rank websites against particular keywords however after a day keywords get clear ranking.

it called Google dance .

Google is updating his algorithm for spam sites so it will be affect our keywords as some sites go down and up.

We think that this occurs because Google routes some search queries during the night to different data centres, perhaps for maintenance reasons. This sometimes results in different rankings because search engine data centres don't always store exactly the same information (they are synchronised routinely, but it's always possible to catch them in an un-synchronised state as well).