I was asked to perform the following task using HTML and CSS. I failed to do so because I had never done any overlapping of objects and so I was unaware that I had to give a parent and child DIVs instead of sibling DIVs and also I didn't consider that moving the box 50% to the middle won't work because the box has length of it's own and won't be exactly in the center on 50%. I figured it out just after the interview. I can now tackle this problem with confidence, shall it present itself again. Success is nothing but a sequence of failures that make u better after each attempt.