Here is the correctly formatted mol file for SO2 including charges in the 6th field. 
Select the lines between the dashed lines, do ctrl-c, then ctrl-v in the WebMO Import box. 
(The first blank line above WebMO must be selected and copied.)
This html page includes the <pre> </pre> tags that preserve the correct spacing in the
.mol file.
-------------------------------------------

  WebMO

  3  2  0        0              1 V2000
   -0.9665    1.2396   -23.901 S   0  1  0  0  0  0  0  0  0  0  0  0
   -2.4251    0.2728   -23.901 O   0 -1  0  0  0  0  0  0  0  0  0  0
    0.3652    0.5767   -23.901 O   0  0  0  0  0  0  0  0  0  0  0  0
  2  1  1  0
  1  3  2  0
M  END
-------------------------------------------