"This Gender Guesser system is heavily based on the Gender Genie. In particular, the word lists and weights are reproduced from the Gender Genie. The Gender Guesser extends the interpretation of informal writing to work on blogs and chat-room messages, and combines formal writing styles (fiction, non-fiction, essays, news reports, etc.). It also looks for weak emphasis -- used to distinguish European English from American English. In general, if the difference between male and female weight values is not significant (a "weak" score), then the author could be European. This is because the weight matrix is biased for distinguishing genders in American English."
I guess it means if the usage of "male" and "female" words is close, then its European English somehow