I cannot fit the page to the screen. The top of the page is not visible and I cannot grab the upper boundary or corner to reduce the size.
Hello,
What OS? With Ubuntu for example, Alt +F7 will allow mouse or arrow keys to move a selected window. This will get the top back in view.
In Windows press Alt+Spacebar, then M a four-sided arrow will appear. Use the arrow keys to move the window.
Or Win+UpArrow will maximise a window to fit full screen