Update references

Author: macobo

docs/ecommerce-revenue-tracking.md

@@ -20,7 +20,7 @@ The revenue metrics are fully filterable. For instance, you can see the total or
 
 You can add multiple filters to [create audience segments](filters-segments.md) too. This allows you to see the conversions and revenue from for instance the audience segment that's located in Germany, Austria and Switzerland, that were referred by a particular UTM campaign and are using Mac OS.
 
-"**Ecommerce revenue**" is an [optional enhanced measurement](script-extensions.md) that's not included in our default script. This is because we want to keep the default script as simple and lightweight as possible. If you want to track ecommerce revenue, here's how to enable it:
+If you want to track ecommerce revenue, here's how to enable it:
 
 ## Step 1: Add a new custom event and specify the currency of your choice
 

docs/error-pages-tracking-404.md

@@ -16,7 +16,7 @@ Tracking 404 error pages is essential for many site owners and Plausible helps y
 * See where visitors find broken links to your 404 error pages
 * Then you can manually fix broken links and redirect error pages
 
-"**404 error pages**" is an [optional enhanced measurement](script-extensions.md). If you want to track 404 error pages, here's how to enable it:
+"**404 error pages**" requires additional work in addition to [setting up tracking script](/plausible-script). If you want to track 404 error pages, here's how to enable it:
 
 ## Paste this piece of code to your 404 page template