add note about best practices for style attribute

content/docs/reference-dom-elements.md

@@ -114,6 +114,8 @@ React will automatically append a "px" suffix to certain numeric inline style pr
 
 Not all style properties are converted to pixel strings though. Certain ones remain unitless (eg `zoom`, `order`, `flex`). A complete list of unitless properties can be seen [here](https://github.com/facebook/react/blob/4131af3e4bf52f3a003537ec95a1655147c81270/src/renderers/dom/shared/CSSProperty.js#L15-L59).
 
+**Note:** Some examples in the documentation use `style` for convenience, but per modern web development best practices, **using the `style` attribute as the primary means of styling elements is _not recommended_.** In most cases, [`className`](#className) should be used to reference classes defined in an external CSS stylesheet. `style` is most often used in React applications to add dynamically-computed styles at render time. 
+
 ### suppressContentEditableWarning
 
 Normally, there is a warning when an element with children is also marked as `contentEditable`, because it won't work. This attribute suppresses that warning. Don't use this unless you are building a library like [Draft.js](https://facebook.github.io/draft-js/) that manages `contentEditable` manually.