how to set SSRS Report parameters to be optional i.e Non-Mandatory field in SSRS 2005

Please help me to set the SSRS Report parameters to be optional i.e Non-Mandatory field in SSRS 2005.

What is the difference between internal and hidden parameters in SSRS?

Hidden – parameter is not presented to end users when running the report, but the parameter can be passed into the report at run time and does show up when setting up subscriptions. Internal – similar to hidden except in addition to not being presented to users running the report, it cannot be passed in a run time.

As Hiten suggested there is nothing exactly we can call as optional parameters but if you want users to see this parameter as optional, use formula or case statements.

Parameterized stored procedures with some defaults or null value can be used to achieve the same goal.