How to Get a Useful Mouse-over/Highlight Translation Addons to Help With Reading (Firefox):

Any language:
wiktionary + google translate with mouse over / other options:
http://www.toptip.ca/2010/10/firefox-extension-google-dictionary-and.html

Just Chinese-->English:
mouse over translation:
https://addons.mozilla.org/fr/firefox/addon/perapera-kun-chinese-popup-tra/