Google Toolbar shows incorrect PageRank for HTTPS pages

If you are a webmaster looking to improve your Google ranking by arranging links from high-PageRank sites, you should be wary of pages whose URL starts with “https” (secure pages). As I have found, the Google Toolbar reports incorrect (usually inflated) PageRank for such pages, so that a secure page which appears to have a PageRank of 8 may in fact have a much lower PR or may not even be indexed at all.

When you visit a secure (https) page, the PageRank you see in the Google Toolbar is not the PageRank of the page — instead, the toolbar shows you the PR of the root page of the domain.

• https://addons.mozilla.org/en-US/firefox/user/1754094 is the user info page for Jose Bolanos, one of the many developers at the Mozilla add-on community website. In both IE and Firefox, it appears to have a PageRank of 8. Now, if that were true, Jose would truly have a reason to smile. Unfortunately for him, what the toolbar is actually showing is the PageRank of https://addons.mozilla.org, the homepage of the add-ons site. If you try any other page on the site (e.g. this one or this one), you will see that they all have a PR of 8.
• The Google Adsense login page (https://www.google.com/adsense/login/en_US/) appears to have a PR of 10 (higher than adobe.com) not because it has so many incoming links or because Google has given it an artificial boost — it’s just that the Google Toolbar is reporting the PR of google.com.
• This obscure page at the Michigan State University and all its subpages appear to have a PR of 8. Of course, by now we know that what we’re really seeing is the PR of the MSU homepage (www.msu.edu) and the actual PR of the page is unknown.

The bug seems to affect the latest versions of the Google Toolbar for IE and Firefox. However, I have seen an earlier version of the toolbar that did not suffer from this problem, so I believe the issue is version-dependent.