You can set mousewheel.with*.action pref(s) to 0 to perform a scroll.

mousewheel.withcontrolkey.action
mousewheel.withnokey.action
mousewheel.withshiftkey.action

To open the about:config page, type about:config in the location (address) bar and press the "Enter" key, just like you type the url of a website to open a website.
If you see a warning then you can confirm that you want to access that page.

• Use the Filter bar at to top of the about:config page to locate a preference more easily.
• Preferences that have been modified show as bold (user set).
• Preferences can be reset to the default via the right-click context menu if they are user set
• Preferences can be changed via the right-click context menu: Modify (String or Integer) or Toggle (Boolean)

Cor-el... Thanks for your suggestion. The note that it might void my warranty makes me nervous... Plus not sure how changing how the mouse moves is going to solve current problem of fonts that are too big (on msn.com) and too small (on cnn.com). Is this just to change it so it's not so sensitive and will it make it stop changing the font size is I do mess with it? All I'm doing is moving the cursor quickly, so don't understand why it changes font size.

Thanks! A total non-techy, so even your directions seem a bit intimidating, and then there is that warning sign...

If you press the Ctrl key and use the mouse scroll wheel then you zoom the page.
It is possible that that action gets triggered some how.

If you set those prefs to 0 then you can no longer zoom the page with the mouse.

If you type mousewheel.with in the Filter at the top of the about:config page then you see all prefs that start with that name.

See also:

• http://kb.mozillazine.org/About:config_entries#Mousewheel.