Below about 600px (phones and small windowed browsers) the sidebar
starts breaking the layout. Moving it inline helps a lot; with
modern CSS (flex layout) we can also shuffle it after the main content.
Older browsers that don't do one of the 4 variants of flex layout
will just display it above the main content, which is annoying
but not too bad.
blueview also has a minimum width set so that it won't become
ridiculously small with small fonts, but that means it gets
scrollbars below about 850px; stop enforcing the minimum width
if necessary.
Finally, blueview's relatively generous margins look good in a
desktop browser, but are just too space-hungry on a phone.
Turn them off below 600px.
Simon McVittie
Amitai Schlair
Jon Dowland
Joey Hess