I can't give you an answer. But, if you click on the middle mouse button, it turns the mouse into a scroll controller.

Many thanks for your prompt answer. My mouse doesn't have third button. It has 4 buttons and different functions can be assigned to each of them. None of them is scroll controller.

What do you mean with one click is a full screen in your question ?

Are you clicking in the scroll bar or are you using the mouse wheel to scroll ?

When I am using the scroll wheel that is around the ball (it is a trackball mouse) and move it only one click, the screen doesn't move just a bit but scroll sup or down a whole screen.

Have you checked the trackball settings? You may need to contact the trackball's support.

When I am using the scroll wheel that is around the ball (it is a trackball mouse) and move it only one click, the screen doesn't move just a bit but scroll sup or down a whole screen.

I'm guessing you have two of the buttons to be like Left and Right clicks on a mouse.

I would likely set one to simulate Middle-click so I can use it for middle-clicking links into a new tab, closing tab and to use the Autoscroll, which is probably what Fred meant by scroll controller.

Hi FredMcD, I use KensingtonWorks for setting the mouse. With other applications it works well. Only on Firefox the scrolling is too excessive. Hi James, I found the middle click setting in KensingtonWorks. I can activate it and it says: "Select Middle Click or a valid key combination of Middle Click key and modifier key(s) to set a shortcut." The modifier keys are: Win, Alt, Shift, Ctrl. Simply activating the Middle click function (not choosing any of the modifier keys) is not really doing anything when I press the button.