Creating a column grid on a page

Help! I am trying to create a column grid on a page. I’d like to be able to insert either a picture or code or both in each slot but don’t know how to do it. In a perfect world i’d like it to be 3 columns wide and unlimited in dept (height). See example of what I’m looking to achieve here.http://www.dessign.net/gridportfolio/ Is this possible with Mantra? Thanks in advance