The Mozilla Toolkit is a set of APIs, built on top of Gecko, which provide advanced services to XUL applications. These services include Profile Management, Chrome Registration, Browsing History, Extension and Theme Management, Application Update Service, and Safe Mode. (More info)
The menu panel and two panels on the new tab page (search engine picker and gear icon) are never position properly anymore on OS X 10.9 and Windows 7 for the last few days.
I will find the regression window.