It's designed around two ideas: 1. A page is tet + images. Complex layouts are very late invention for HTML 2. The whole layout can be done in a single pass.

It's designed around two ideas: 1. A page is tet + images. Complex layouts are very late invention for HTML 2. The whole layout can be done in a single pass. This was crucial for the 90-s era browsers because you wanted to be fast on rather underpowered machines. I think double-pass was permitted/mentioned in standards only around 2000/2001 with relation to tables (I forget what it was exactly). Centering an element vertically may require several passes (do the rest of the layout, layout the component, layout the component centrally, possibly reflow the rest of the document, etc.), and it was a big no-no