Because of the nature of Page Rank, the calculations need to be performed about 40 times and, because the index is so large, the calculations take several days to complete. During this period, the search results fluctuate; sometimes minute-by minute. It is because of these fluctuations that the term, Google Dance, was coined. The dance usually takes place sometime during the last third of each month.
Google has two other servers that can be used for searching. The search results on them also change during the monthly update and they are part of the Google dance.
For the rest of the month, fluctuations sometimes occur in the search results, but they should not be confused with the actual dance. They are due to Google’s fresh crawl and to what is known “Everflux”.
Google has two other searchable servers apart from www.google.com. They are www2.google.com and www3.google.com. Most of the time, the results on all 3 servers are the same, but during the dance, they are different.
For most of the dance, the rankings that can be seen on www2 and www3 are the new rankings that will transfer to www when the dance is over. Even though the calculations are done about 40 times, the final rankings can be seen from very early on. This is because, during the first few iterations, the calculated figures merge to being close to their final figures.
You can see this with the Page Rank Calculator by checking the Data box and performing some calculations. After the first few iterations, the search results on www2 and www3 may still change, but only slightly.
During the dance, the results from www2 and www3 will sometimes show on the www server, but only briefly. Also, new results on www2 and www3 can disappear for short periods. At the end of the dance, the results on www will match those on www2 and www3.
GOOGLE Dance Tool
This Google Dance Tool allows you to check your rankings on all three tools www, www2 and www3 and on all 9 datacenters simultaneously.
The Google Web Directory works in combination of the Google Search Technology and the Netscape Open Directory Project which makes it possible to search the Internet organized by topic. Google displays the pages in order of the rank given to it using the Page Rank Technology. It not only searches the titles and descriptions of the websites, but searches the entire content of sites within a related category, which ultimately delivers a comprehensive search to the users. Google also has a fully functional web directory which categorizes all the searches in order.