Thank you for the picture, which has helped.
This is not a jD bug but regular Joomla! behaviour. Atthached are three pics. The first one is from the Joomla! Global Config where it shows wheter or not you wish to see the site name, which is also given in the Joomla! Global Config -site settings tab.The other part of the text shown in the browser tab comes from the title of the active menu item.This is illustrated in the other two pics.
So not a jD bug but just regular Joomla! behaviour.ColinPS have moved this topic to General