Don't try to see open source as a threat, but as an advantage. When a very critical bug was discovered that affected Mozilla/Firefox/Thunderbird, an update to fix this problem was available within 48 hours. Could you give me an example? Firefox allows plugins (aka "extensions") and visual themes to be installed. A couple of popular extensions such as Adblock (advertisement blocker), All-in-one Gestures (allows you to control the browser with mouse gestures) or Web Developer are available. MozBackup can take care of that. It works for Moz/FF/TB. Example? I haven't noticed any problems with sites which use BIG5(HKSCS) or SHIFT_JIS. This also depends on the doctype that needs to be specified.