Hi Willomina. Welcome to the forums.
Hm, the page is way too wide for most screens (100em is too much). You basically have a fixed width layout here, apart from the footer, which is nicer, because it stretches/contracts to fit the window.
Firstly, avoid using position: absolute for page layouts. it's deadly, really. Absolute elements don't flow nicely with ther parts of the page, making updates miserable.
% is often better than em, though a combination of them works nicely.