Fix bad links in docs. Fixes #3654.

tips/17-children-undefined.md

@@ -25,4 +25,4 @@ var App = React.createClass({
 React.render(<App></App>, mountNode);
 ```
 
-For a more sophisticated example, refer to the last example on the [front page](/).
+To access your own subcomponents (the `span`s), place [refs](/react/docs/more-about-refs.html) on them.

tips/19-dangerously-set-inner-html.md

@@ -21,4 +21,4 @@ The point being that if you unintentionally do say `<div dangerouslySetInnerHTML
 
 This functionality is mainly provided for cooperation with DOM string manipulation libraries, so the HTML provided must be well-formed (ie., pass XML validation).
 
-For a more complete usage example, refer to the last example on the [front page](/).
+For a more complete usage example, refer to the last example on the [front page](/react/).