Not sure if I’m misunderstanding the question, but are you asking how to launch a web browser from the AS400 or how to specify parameters when you launch it?
To launch a browser you can use the STRPCO and STRPCCMD commands (assuming you have iSeries Access installed). There was a thread on this in February 2007 in the Midrange.Com archives that gave a command (source at http://www.astradyne-uk.com/code/index.php?id=66648adc5e) to launch a browser using the STRPCO and STRPCCMD commands.
To add parameters to the launch you would do it the same way you would for any CGI program by tacking them on to the end of the URL. For example:
Where the “?” separates the parameters from the URL, the “=” separates the parameter name and the value, and the “&” separates parameter pairs.
Hope it helps