Hi Dale, classic zooming can be reset by holding down the Command key and tapping 0 (that's a zero) or clicking the zoom percentage button in the address bar. However, your Firefox might be doing the other kind of zooming, similar to pinching apart on a trackpad. Normally, just moving the mouse wouldn't trigger pinch/magnification zooming; I wonder whether it somehow got connected with a particular gesture. Could you take a look at these preferences: (1) In a new tab, type or paste '''about:config''' in the address bar and press Enter/Return. Click the button promising to be careful or accepting the risk. (2) In the search box above the list, type or paste '''mousewheel*action''' and pause while the list is filtered Firefox will display numerous matches. This is my understanding of what maps to what on Mac. The "override.x" preferences are for horizontal scrolling gestures. You could try changing those to 0 (do nothing) and see whether it makes any difference. <table> <tr><td>'''Preference'''</td><td>'''Key'''</td><td>'''Mac Default Action'''</td></tr> <tr><td>mousewheel.default.action</td><td>--</td><td>1 => Scroll normally</td></tr> <tr><td>mousewheel.default.action.override.x</td><td>--</td><td>-1 => Same as above</td></tr> <tr><td>mousewheel.with_alt.action</td><td>Option/Alt</td><td>2 => Back/Forward in History</td></tr> <tr><td>mousewheel.with_alt.action.override.x</td><td>Option/Alt</td><td>-1 => Same as above</td></tr> <tr><td>mousewheel.with_control.action<br>''</td><td>Ctrl</td><td>3 => Zoom in/out (reflowing)</td></tr> <tr><td>mousewheel.with_control.action.override.x<br>''</td><td>Ctrl</td><td>0 => Ignore</td></tr> <tr><td>mousewheel.with_meta.action</td><td>Command</td><td>3 => Zoom in/out (reflowing)</td></tr> <tr><td>mousewheel.with_meta.action.override.x</td><td>Command</td><td>0 => Ignore</td></tr> <tr><td>mousewheel.with_shift.action</td><td>Shift</td><td>1 => Scroll normally</td></tr> <tr><td>mousewheel.with_shift.action.override.x</td><td>Shift</td><td>-1 => Same as above</td></tr> </table> (3) Double-click the preference you want to modify and enter the desired value from the following list. After making the change, click the blue checkmark button or press Return to complete the edit. * 1 = Scroll normally (ignore the modifier key) * 2 = Go Back/Forward in history (dangerous?) * 3 = Zoom in/out (reflowing zoom) * 4 = Switch to horizontal scroll * 5 = Zoom in/out (pinch/magnfy zoom) * 0 = Do nothing

Some good information, however to problem still is occurring sporadically. Changed both control.action and meta.action preferences to 0, and the frequency seems to be somewhat less. Interesting the term "mousewheel" is used with the Apple wireless mouse. I think of "wheel" being more associated with Microsoft!