docs section for non-dom attributes

Also added documentation for `dangerouslySetInnerHTML`.

_data/nav_docs.yml

@@ -55,3 +55,5 @@
     title: Event System
   - id: dom-differences
     title: DOM Differences
+  - id: special-non-dom-attributes
+    title: Special Non-DOM attributes

docs/ref-04-tags-and-attributes.md

@@ -57,7 +57,9 @@ rowSpan scrollLeft scrollTop selected size spellCheck src step style tabIndex
 target title type value width wmode
 ```
 
-In addition, the non-standard `autoCapitalize` attribute is supported for Mobile Safari.
+The non-standard `autoCapitalize` attribute is supported for Mobile Safari.
+
+In addition, there is the React-specific attribute `dangerouslySetInnerHTML` ([more here](/react/docs/special-non-dom-attributes.html)), used for directly inserting DOM strings into a component.
 
 ### SVG Attributes
 

docs/ref-06-dom-differences.md

@@ -4,6 +4,7 @@ title: DOM Differences
 layout: docs
 permalink: dom-differences.html
 prev: events.html
+next: special-non-dom-attributes.html
 ---
 
 React has implemented a browser-independent events and DOM system for performance and cross-browser compatibility reasons. We took the opportunity to clean up a few rough edges in browser DOM implementations.

docs/ref-07-special-non-dom-attributes.md

@@ -0,0 +1,13 @@
+---
+id: special-non-dom-attributes
+title: Special Non-DOM Attributes
+layout: docs
+permalink: special-non-dom-attributes.html
+prev: dom-differences.html
+---
+
+Beside [DOM differences](/react/docs/dom-differences.html), React offers some attributes that simply don't exist in DOM.
+
+- `key`: an optional, unique identifier. When your component shuffles around during `render` passes, it might be destroyed and recreated due to the diff algorithm. Assigning it a key that persists makes sure the component stays. See more [here](/react/docs/multiple-components.html#dynamic-children).
+- `ref`: see [here](/react/docs/more-about-refs.html).
+- `dangerouslySetInnerHTML`: takes an object with the key `__html` and a DOM string as value. This is mainly for cooperating with DOM string manipulation libraries. Refer to the last example on the front page.