Because the sites that were linking to you had their PR changed once Google made another PR update. Some increase, some decrease. If you get PR9, don't dream that it will stay like that. I had one site decreasing from 1 to 0 and another one from 1 to 3! --Commy
yah its true because my website is PR4 but suddenly it become zero... how can i fix this and be back to its normal PR
Many of us still confusing on what is the basis why google sucks the PR of innocent sites. I mean sites that did not sell links. Hopefully Google will address some unanswered questions about this issue.