[Dev-C++] problem with warning message in cpp

Dear friends,
                In vc++ compiler i'm getting this warning. Please any one can help me why this warning is comming and how to avoid it. 
 
warning C4091: 'typedef ' : ignored on left of 'class std::vector<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >,class std::allocator<class std::basic_string<char,struct
 std::char_traits<char>,class std::allocator<char> > > >' when no variable is declared
 
I'm using definitions like 
typedef vector<string,allocator<string> > vec;
typedef pair<short,short> location;
typedef vec<location,allocator<location> > locations_def;
typedef pair<vec*,locations_vec*> text_locations_pair;
 
in my program. 
 
Another question is why to give space at last in vector defintions in vc++ compiler 
why vector<string,allocator> will not work in this compiler. 
 
If you've answers please mail me and help me
 
Thanking you,
 
yours sincerely,
bhadram

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