The key is using width: auto; overflow: auto; -- this allows the div(s) to the
left of the floating sidebar to be resized to fit next to it, and prevents
any clear: both from pushing the div down below the end of the sidebar.
Many thanks for the Hurd wiki's developers for originally figuring this out.
The edit page recently developed the same problem with its textarea, now
that a sidebar can appear on that page too. In editpage.tmpl I needed to
add a new div around the editcontent textarea, as the above styles cannot
be applied directly to textareas. The textarea's own width is reduced to
98% because at least in chromium this avoids it getting unnecessary
horizonatl scrollbars when a sidebar is displayed next to it.
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