Hello,

Try disabling graphics hardware acceleration. Since this feature was added to Firefox, it has gradually improved, but there still are a few glitches.

You might need to restart Firefox in order for this to take effect, so save all work first (e.g., mail you are composing, online documents you're editing, etc.).

Then perform these steps:

• Click the orange Firefox button at the top left, then select the "Options" button, or, if there is no Firefox button at the top, go to Tools > Options.
• In the Firefox options window click the Advanced tab, then select "General".
• In the settings list, you should find the Use hardware acceleration when available checkbox. Uncheck this checkbox.
• Now, restart Firefox and see if the problems persist.

Additionally, please check for updates for your graphics driver by following the steps mentioned in the following Knowledge base articles:

Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems

Upgrade your graphics drivers to use hardware acceleration and WebGL

Did this fix your problems? Please report back to us!

Thank you.

In order to be able to find the correct solution to your problem, we require some more non-personal information from you. Please do the following:

• Click the Firefox button at the top left, then click the Help menu and select Troubleshooting Information from the submenu. If you don't have a Firefox button, click the Help menu at the top and select Troubleshooting Information from the menu.

Now, a new tab containing your troubleshooting information should open.

• At the top of the page, you should see a button that says "Copy text to clipboard". Click it.
• Now, go back to your forum post and click inside the reply box. Press Ctrl+V to paste all the information you copied into the forum post.

If you need further information about the Troubleshooting information page, please read the article Use the Troubleshooting Information page to help fix Firefox issues.

Thanks in advance for your help!

There have been changes to the mousewheel prefs as the consequence of implementing DOM3 mouse wheel scrolling (Bug 719320).

I don't think that it is possible to override / set the scroll amount when using a modifier key to a specific number of pixels.

There are only delta multipliers that modify the number of lines (33 changes the scroll amount to one third), so probably the closed that you can get is to set the action for the Alt modifier to 1 (i.e. 1% of the default).

You can modify mousewheel.*.delta_multiplier_y prefs (vertical Y-axis) to change the vertical scroll amount.

• mousewheel.system_scroll_override_on_root_content.enabled -> true
• mousewheel.with_control.delta_multiplier_y

That's it!! Thank you very much for your help!! I've changed the delta_y to:

mousewheel.with_alt.delta_multiplier_y = 2

and now I can again scroll by 1 pixel the same way as before updating the FF (with Alt+mouse wheel).

delta_y = 1 was to low - I had to turn the wheel 2 or 3 times to scroll by 1 pixel, then I tried 5, 4, 3 and 2 and 2 seems to be the best match.

Thank you again,

Regards