i was experimenting with making an aside for a probably overcomplicated cohost post. i'm not sure i'll finish the original post, but i thought i'd share the code in case it's useful. no tricks here, just some fiddling to get it to match the rest of cohost.
in case you're not that familiar with HTML, just change the part between <aside> and </aside>. or to make it slightly simpler, ignore the first and last lines and just change the text inside to whatever you want.
note that the height of the sample above is due to the content being short; the sidebar will grow to fit the content and happily extend past the rest of your post if it gets too long.
the code:
<aside style="float: right; margin-left: 0.5em; width: 33%; padding 0.5em; border: 0.25rem solid lightgrey;">
As a matter of fact,
</aside>