As with any Windows program, you can maximize the window, or you can size it manually. To more modestly size the browser, make sure you are not in Full Screen mode (F11 will switch between regular and full screen) and not maximized. If you still cannot resize the window by dragging the edges, you may be in a dialog window, which is a window opened by a script in a page. Try pressing Ctrl+n to open a new, normal window which you then can resize just like any other Windows program. Does that work?