FF by default runs on multiple processes so if you're running into an issue that crashes a tab you're not likely to lose all of them. however, you can turn this off by adjusting '''webgl.cgl.multithreaded''' in '''about:config''' which should restrict it to a single process. As for the memory, most browsers use quite a bit, just through the process of keeping webpages going with all the junk they have nowadays, unfortunately.