Firefox and Google Reader Icons

I noticed for a long time behind firelight (I did not check it on others) of strangeness in displaying the Reader's icon in the bookmarks bar. If the bookmark refers to http : //www.google.com/…, then the icon on the bookmark matches the favicon of the page: , but if the link has the form https : //www.google.com/…, then we already see the application icon, which is up to 16x16: (immediately and not see what is on it). But this is not all: it tends to change spontaneously both to the native favicon and to the colorful icon of Google.