css - Apply style to element, only if a certain element exists next to it -

i'm using <section> tag on several pages, on 1 page i'm using <aside> tag preceded <section> tag.

in case have <section> followed <aside>, apply width both , have section float left, , aside float right.

basically, if have <section> , <aside> want style work this:

section {     width: 500px;     float: left;     padding: 8px; }  aside {     padding:8px;      width:400px;     float:right; }

if have <section> want like:

section {     padding: 8px; }

is there way can either conditional statement in css3, or pseudo-class, without having use javascript, custom classes, or separate css files?

this works if <section/> comes after <aside/>:

<aside>content</aside> <!-- if there node in between, use '~' selector --> <section>content</section>

in case use aside ~ section or aside + section:

section {     padding: 8px; } aside + section {     width: 500px;     float: left; }

in other cases you'll have use javascript because these selectors work in 1 direction, top bottom.

~~with css4 there might way using subject of selector child combinator, that's future.~~ selector removed specification.

Bready