if i purchase portal via steam can i play offline? and if so how do you go about it and how do you tell what games can do that?
Yes you can play Portal offline on Steam. Open Steam client, you should see a menu bar that has "Steam" "Friends" etc. etc. Click "Steam" and you should see a "Go Offline". Click that. It will say it needs to restart, just click "Restart in offline mode". Basically every game can do that except those games that have the "Multi-player" label on it like Team Fortress 2. Hope that helps.
Thanks but two more questions... That applies to macs as well as pcs? and do you have to originally boot online to go off. (do you need internet from the start?)
Yes it applies to mac as well as windows. You also need an Internet connection to boot online. If you don't have an Internet connection however, it will prompt you to start in offline mode.
