an argument is positive from stackpointer (esp+xxx)
a local is negative from stackpointer (esp-xxx)
ida renames all locals ie DWORD ptr ss:[esp-xx] as var_xxx
and all argumts ie DWORD PTR SS:[esp+xxx] as arg_XX
you can mass rename them with a script or use K keyboard shortcut to see a single instance
i had a few posts on how you can mass rename it here and here
EDIT
or you can change the ANALYSIS kernel option 1
uncheck create stack var
or open ida.cfg and change the analysis option = 0xffff to 0xfbff and ida wont create those vars and args
:\>echo %cd%
E:\IDA_FREE_5\cfg
:\>grep -n ANA.*FBFF *
ida.cfg:194:ANALYSIS = 0xFBFF // This value is combination of the bits defined