fix link to custom scripts

_version_4/3-usage.md

@@ -24,7 +24,7 @@ This page contains some common examples of how to use the PHP PhantomJS library.
 * [PhantomJS Options](#phantomjs-options)
 * [Exceptions](#exceptions)
 
-For more advanced customization or to load your own PhantomJS scripts, see the [custom scripts]({{ site.BASE_PATH }}/4.0/custom-scripts/) section.
+For more advanced customization or to load your own PhantomJS scripts, see the [custom scripts]({{ site.BASE_PATH }}/4.0/4-custom-scripts/) section.
 
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