Hello Dear The "Google Dance" would happen anywhere up to 36 times per year, however in 2003 Google begun updating its index on a weekly basis, which all but eliminated the Google Dance... I hope this info was useful 4 U......
When Google update their database ,the search engine result pages returned by it's many data centers, So from all of them some showing the new results as well as some are showing from old database and this search engine result page placement of a site will change while minute to minute and this is referred to as Google dance.
This discussion will help you - http://forums.digitalpoint.com/showthread.php?t=2296371&highlight=google+dance
when your site jumps from one postion to other in page raking on google regulary in short spam of time,this is claaed google dance.
When google update its search index.., then you might see some difference in your SERP's..,i think this is called as Google Dance..,
Google dance is provide as a tool to help you,the webmaster determine when the google search engine is spidering the internet.Google dance has often been used to describe index update of the google search engine.Google dance where happen anywhere up to 36 times per year.Google dance can always be watched at the test doamin.
Google dance is simply the fluctuation in ranking. Your search rank can be fluctuated however it's not stay longer. It can be occurred for several reasons like if you don't update your site for a long time or your site doesn't indexed properly.