Does this issue occur only on Firefox?

Ensure all hardware for your mouse is up-to-date.

Try Firefox Safe Mode to see if the problem goes away. Safe Mode is a troubleshooting mode, which disables most add-ons.

(If you're not using it, switch to the Default theme.)

• On Windows you can open Firefox 4.0+ in Safe Mode by holding the Shift key when you open the Firefox desktop or Start menu shortcut.
• On Mac you can open Firefox 4.0+ in Safe Mode by holding the option key while starting Firefox.
• On Linux you can open Firefox 4.0+ in Safe Mode by quitting Firefox and then going to your Terminal and running: firefox -safe-mode (you may need to specify the Firefox installation path e.g. /usr/lib/firefox)
• Or open the Help menu and click on the Restart with Add-ons Disabled... menu item while Firefox is running.

Once you get the pop-up, just select "'Start in Safe Mode"

If the issue is not present in Firefox Safe Mode, your problem is probably caused by an extension, and you need to figure out which one. Please follow the Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems article for that.

To exit the Firefox Safe Mode, just close Firefox and wait a few seconds before opening Firefox for normal use again.

Please report back soon.

Is the scroll wheel for this mouse sensitive to movements?

If it is, it may just be when you push the scroll wheel is it moving and causing the page to scroll.

If possible, try the same mouse on a different computer.

Note that you can press the Home key to scroll to the top as a temporary workaround.

I would assume that this is either a problem with a Firefox extension or a problem with a setting in the mouse driver software.
Can you try a different mouse?

Boot the computer in Windows Safe mode with network support (press F8 on the boot screen) as a test to see if that helps.

Thanks for taking time to explain. I've opened Firefox on Safe Mode and the mouse continued to work same way. So it is not related to any add-on. The mouse softwares are the latest ones. I am sure I am not scrolling the wheel when clicking it. I tried many times with extreme caution but no, I am not the reason.

After your suggestions I borrowed and connected a wireless Microsoft mouse. I didn't have any problem with middle click (only the wheel scrolling was very slow as I've disabled hardware acceleration etc. which is normal)

So my guess is, rather 1. I have a wrongly functioning mouse (but in other programs, I don't face such problem) or 2. There is a compatibility issue with the Logitech software and Firefox.

Did you check the settings in the Logitech mouse driver?

Boot the computer in Windows Safe Mode with network support (press F8 on the boot screen) as a test to see if that helps.

The middle mouse button (scroll wheel) can be pressed down as well as to the left and right. If these left and right buttons are accidentally pressed when you try to open a new tab it could be causing the scroll down problem. In chrome these left and right buttons act like the home and end keys and take you to the top and bottom of the page. My suggestion, try to avoid pushing the scroll wheel on an angle.

This no longer seems to affect firefox, but perhaps it will help out people using other browsers as well.