I use iwebtool to check a PR of 3.8, it predicts PR 4 So the pr 3.5 to 4.5 is equal to pR4? What's the difference between pr 3.5 and 4.5? just difference of back links?
Not just backlinks but a no. of other factors like how crawlable your pages are. the visual PR is just a lig factor of the real PR, which is a very high decimal no like xxxxxxxxxxx. The visual PR is given based on median value of the factor.
I was under the assumption that PR 3.99999999999999 is still a PR3 on the toolbar and that those PR prediction tools don't work.