As Shariq said, "further" has all the meanings of "farther," plus "further" has additional meanings. Check out Grammar Girl, as Bridget suggested, but the quick fix is to simply never use "farther," since it can always be replaced by "further."

Both farther and further are used to express distance. Also, further is used to mean "additional". ex- After this he made no further remark. kazakhistan is farther/further from the equator than India. :)

Farther --- distance Further --- events

Farther when there is a physical distance: "I want to go farther", further when there is a figurative distance, something that you can't touch or measure: "he was my friend but he went further with his actions"

Hey Markhabat - I don't think I can explain it any better than Grammar Girl: http://www.quickanddirtytips.com/education/grammar/further-versus-farther She has awesome answers to questions like this!