hello pikashi, the scrolling behaviour was overhauled in firefox 17 (for technical reference see [https://wiki.mozilla.org/Gecko:Mouse_Wheel_Scrolling]). it should still be possible to set a different scroll speed when the alt-key is pressed. you can enter '''about:config''' into the firefox location bar (confirm the info message in case it shows up), search for the preferences starting with '''mousewheel.with_alt.delta_multiplier_''' ... you can double-click those settings & assign a different value to them - then a restart of firefox is required for changed settings to take effect in the browser. i'm not exactly sure how they work, but for example by setting them all to 33 instead of 100 the scrolling speed is considerably reduced. you might want to play around a little bit to find the ideal values that fit your need...

It's ok now, thank you very much!