fix #767; update README

Author: mbostock

README.md

@@ -88,7 +88,7 @@ The default **width** is 640. On Observable, the width can be set to the [standa
 
 The default margins depend on the plot’s axes: for example, **marginTop** and **marginBottom** are at least 30 if there is a corresponding top or bottom *x* axis, and **marginLeft** and **marginRight** are at least 40 if there is a corresponding left or right *y* axis. For simplicity’s sake and for consistent layout across plots, margins are not automatically sized to make room for tick labels; instead, shorten your tick labels or increase the margins as needed. (In the future, margins may be specified indirectly via a scale property to make it easier to reorient axes without adjusting margins; see [#210](https://github.com/observablehq/plot/issues/210).)
 
-The **style** option allows custom styles to override Plot’s defaults. It may be specified either as a string or an object of properties (*e.g.*, `"color: red;"` or `{color: "red"}`). By default, the returned plot has a white background, a max-width of 100%, and the system-ui font. Plot’s marks and axes default to [currentColor](https://developer.mozilla.org/en-US/docs/Web/CSS/color_value#currentcolor_keyword), meaning that they will inherit the surrounding content’s color. For example, a dark theme:
+The **style** option allows custom styles to override Plot’s defaults. It may be specified either as a string of inline styles (*e.g.*, `"color: red;"`, in the same fashion as assigning [*style*.cssText](https://developer.mozilla.org/en-US/docs/Web/API/CSSStyleDeclaration/cssText)) or an object of properties (*e.g.*, `{color: "red"}`, in the same fashion as repeatedly calling [*style*.setProperty](https://developer.mozilla.org/en-US/docs/Web/API/CSSStyleDeclaration/setProperty)). Note that unitless numeric values such as `{fontSize: 20}` are not supported by CSS; you must specify a string with units such as `{fontSize: "20px"}`. By default, the returned plot has a white background, a max-width of 100%, and the system-ui font. Plot’s marks and axes default to [currentColor](https://developer.mozilla.org/en-US/docs/Web/CSS/color_value#currentcolor_keyword), meaning that they will inherit the surrounding content’s color. For example, a dark theme:
 
 ```js
 Plot.plot({