Tea contains more caffeine weight for weight, but you use less tea to make a cuppa than you do coffee. So a cup of coffee usually has more caffeine than a cup of tea.
according to the international coffee organisation (!) the average cup of brewed coffee has 85mg of caffeine in (percolated has less than dripped), the average cup of instant coffee has 71mg. The average cup of tea contains 60mg but this depends on strength: a strong cup of tea may have more caffeine than a weak cup of coffee.
http://www.ico.org/acoff/caffeine.htm