Insure landing page

This goal of this project was mostly to "stay warm" while I was very busy with my main job (unrelated to web development). However, I do have a question about best practices regarding how to deal with the position of sidebar menus. I always feel unsure when to use fixed vs absolute position, and I usually just go with the one that seems to make fewer problems for me. I guess, more fundamentally, I need to study the difference between the two so I can better understand there contexts.