sidebar borders don’t go down all the way

I am trying to create a 3-column blog. I have a main content area on the far left, then two sidebars to the right. My problem is that I want borders seperating the 3 sections, and the borders on the sidebars only go down as far as the content in the sidebar, which isn’t as long as the main content area. Is there a way to fix this? Here is a link to my log