Why does search results change sometimes a name comes first ,at other times i cant even find it?

the results are displayed based on ranking and relevancy .





so when many users search for a particular word(s) and in the obtained results , if the select the third or fourth , etc option leaving the first one behind, the first result being showed will loose its' ranking and hence will be take a position of 100,200,etc or maybe out of the results... because of which you may not find it.

chinese martial arts