You will find many good references if you go to
http://support.sas.com and then search for:
download csv
The key is to create to a streaming stored process that sets the appropriate MIME headers. Give this (untested) code a try:
[pre]
%let RV=%sysfunc(appsrv_header(Content-type, application/vnd.ms-excel));
%let RV=%sysfunc(appsrv_header(Content-disposition, %str(attachment; filename=temp.csv)));
ods listing close;
ods csv file=_webout;
proc print data=sashelp.class; run; quit;
ods csv close;
[/pre]
Vince DelGobbo
SAS R&D