what does "you don't say"mean? and how to use it?

American drama im into the american drama "bones" very much recently,the face structure of the actress is cubic(can i say so?ha~).i like the friendship between bones and booth.i think it is better to be friends rather than lovers for them.my friend told me teeth is the hardest bones of our body,is that true? ps:i want to say thank you to iangreen for aswering my question.i don't know how to reply him in Q&A section,,,,,o(╯□╰)o........

the city i think the city im living in is a good place for travelling, but not for living, terrible weather....it is said that there is no spring in this city, cuz it is too short. and i think, there is no autumn either, cuz it is as hot as summer now and winter is coming soon. plus, the mid-autumn day is coming~haha~enjoy the short holiday with my friends ~^.^~

Good news & Bad ones Good: the new oriential called me to go to the second round interview, such a big surprise, and such a big challenge to me~~~ Bad: a little insect climbed on my table in a sudden, gave me a scare, i dont like insects, all of them~~!!~~~~(>_<)~~~~