Is there some html code I can put in a page that would dictate how long the lines of text can be?
I want to do this because the fixed width of the main body text in most themes is narrower than I want (i.e. the margins are too wide).
On the other hand, there are themes such as 'Silver Is the New Black' which make the lines run almost the width of the browser window (minus the widget zone), which is longer (wider) than I want.
Those are the only two choices in the available themes, AFAIK: roughly 6 inches on most themes; or, full-screen-width on a couple of the themes.