There are three kinds of
In fact, Second, if
, the first search engine itself: search engine is a complex system, should be included and a lot of new grab page every day, with its own algorithm and is changeable, so sometimes itself can also be a problem, especially when testing the new algorithm, the snapshot often large area correction, sometimes included will be dropped.
snapshot backwards three
third occurred in the third case, if the individual owners, or the new space and domain name back to the station is better. If it is K, the recovery is a need long time, not to do faster station, if it is a slight drop right, then you need to find the reason, is because of the black chain or keyword, because group >