I just changed my theme from Neat to Twenty Eleven because I thought the new theme made it more visually appealing and easier to read. One problem, under my old theme, my sidebar that included widgets for calendar, links, categories, etc. remained static at the top of the blog even as new entries were added. Under the new theme, the sidebar seems to have disappeared, although if I scroll down, I see a list of categories, but that seems to move as I scroll. How do I return the sidebar to its original position and keep it fixed in place?