Frequently asked questions DF™ PR/Alexa Checker
There are plenty of sites for which Google Toolbar does not show any PageRank. When these sites are visited, the toolbar PR meter remains grey. Most PR-checkers return 0 for such sites, while this is not quite correct. When a site has zero PageRank, the Google Toolbar meter is white, not grey.
For example, there is a newly created page called page.html, for which the PageRank value cannot be determined by the toolbar. Still, www.some.com has PR=4 on its main page. Assigning zero PageRank to page.html, as most checkers do, means that this page is equal to sites with zero PageRank which contain no valuable information. To avoid this, improved PageRank detecting mode was implemented. The checker assigns a predicted PageRank value for such an undetected page.