On 2 of my sites I have had Google Page Ranks of 4 for the longest time. All of a sudden a couple weeks ago I noticed that now they have no ranking. Any idea why a site would drop from 4 to 0 over night??
Doubt it was over night...after the PR update, the Big G may have realised that your sites weren't linking to any high PR sites that were previously passing some of their "PR Juice" towards your site. Now perhaps, they've gotten rid of your link, maybe buried in deep inner pages, or just no-follow links... It's not too costly to bring PR back up...just need to get Do-follow links from high PR sites, go to the Buy, Sell, Trade >> Links secteion to get good deals! Hope that helps
Maybe you can list the sites here. I might help as I am a seo specialist. Beware of such sudden drops. It might be worst then you think. You can pm me them if you don't wish to share them here.
This happened to me a few months ago. Was a PR3 and then went to 0 for about 2 - 3 months. We were reset to PR4 last week. I assume it had to do with selling links but I am not 100% certain. I did reapply with google to be reinstated, never heard either way though.