I created a child style.css file as well, and adjusted the dimensions of the container to 1060 to allow room for an extra column. I shrank the #content to 580px and reduced the original sidebar as well. I changed the #content from float: left to float: none and a left margin of 170 to allow room for the left sidebar. The widths of the sidebars and content, with margins and padding, add up to less than the 1060 width of the container.
I added this to the index.php file, above the <div id=”content”> section:
So, the left sidebar I created is showing correctly, not pushed down. However, the right (original) sidebar is being pushed down below the content, even though there is plenty of room for it in the container.