Make sure that you do not press the Ctrl key while scrolling the page with the mouse wheel. You may also need to check the mouse settings in Control Panel > Mouse ---- Other things that need your attention: Your above posted system details show outdated plugin(s) with known security and stability risks that you should update. # Shockwave Flash 10.0 r45 # Next Generation Java Plug-in 1.6.0_23 for Mozilla browsers Update the [[Managing the Flash plugin|Flash]] plugin to the latest version. *http://kb.mozillazine.org/Flash *http://www.adobe.com/software/flash/about/ Update the [[Java]] plugin to the latest version. *http://kb.mozillazine.org/Java *http://www.oracle.com/technetwork/java/javase/downloads/index.html (Java Platform: Download JRE)