How to create a user with minimalistic permissions on OpenBSD?

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http://unix.stackexchange.com – I want to run the webbrowser with a different user on OpenBSD (different from the one I use daily). I will reach the Browser with ssh -X in the local machine. No audio, no flash, no html5, etc. is needed. How can I create a user with the smallest possible permissions? Are there any tricks? (does the user only needs to be in his group, and not else?) (HowTos)