my macs at the mercy of others

hi
yesterday the work computers went down (stupid pc's) i was forced to use my mac to keep everything moving. it's a partnership.however, there will be others using my macbook 5 today until the pc's are up again.i want to know how do i set my mac up so they can view sites, but not be able to download anything?

Go into System Preferences > System > Users & Groups, unlock the padlock using your password, and establish a Guest Account and leave it running in that. You can delete that account later. So far as downloading do not give them the password to get connected.