There are several parameters that can be passed in to the SRS Report viewer through query string parameters. Some of them are listed below:
Change the way it is rendered:
rs:Command=Render& (4 types of re:Commands)
Pass in parameter values:
PARAMNAME1:isnull=true&PARAMNAME2=PARAMVALUE2&
Control the type of output:
rs:Format=PDF
Control what toolbar(s) show in the viewer:
rc:Toolbar=False
rc:Parameters=False