Could it be that Trello default changed and that there is a new left column containing the names of the lists in my board? or is it a setting in this specific board? I can't find how to make the board left-justify, so that the first column is the leftmost vertical element on the board. Any help is appreciated! thanks :)
The "left column" is the "list guide" (more info at http://blog.trello.com/board-and-list-subscribe-desktop-notifications-edit-comments-and-more/)
You should be able to hide it by clicking the bar that appears when you hover the mouse to the right of the list guide.