Need Help with CSS Margins, i added a outline and colums go down

Hi there i added some outline to a 3 colums portfolio and now it became a two colums cause of the outline the third colum is going to another line, ive been looking were is the code to set the margin between colums 2px smaller, but i have tried everywere with no luck, anyone can help point me in the right direction to do this?

here link for homepage were you can see the error

and the portfolio