Has anyone else experienced this? I have now seen 3 of my sites with very strong rankings in Google (top 5 for many competitive keywords) disappear completely one day and then immediately reappear the following day right back to where they belong. Each site experienced this once. I don't sell links on these sites, they are not blogs, I don't do anything black hat. Strange things going on with Google these days...
That's what you call a google dance. It was because google maintains several data centers that feed information into Google search, and these systems must be periodically updated with new Web sites. Rather than taking all of Google off-line when the index is updated, Google takes one data center at a time off-line and updates them individually.
I think it is part of google update. No one knows when is the next PR update....we are just like waiting for nothing...