> But I encounted a problem. When I downloaded a 
> webpage about solar system :
> ..
> the program downloaded many files from other servers
> like nasa, Arizona Univ. and so on. So the number of
> ..
> All the unexcepted files seemed to be pictures

This totally normal, as the default filters are 
something like:
+*.gif +*.jpg +*.png +*.css

Just remove them and it'll work!