A friend of mine has forwarded to my CERN e-mail account an e-mail containing pictures some of which are sexually explicit. May I forward it to colleagues and friends at CERN?

No. You should avoid actions that could create a hostile work environment or make others feel uncomfortable in the office. Giving sexually explicit pictures to colleagues at CERN could constitute harassment, and may also violate the CERN Computing Rules, as set out in Operational Circular No. 5.

(use of professional e-mail accounts)