change url to js.org-hosted domain

docs/guide/effectiveness.md

@@ -29,4 +29,9 @@ Imagine I can send 10,000 emails to 10,000 random recipients for $1. If I can ea
 
 By applying similar concepts to CAPTCHA, we make it costly for bots to spam, effectively discouraging them from trying.
 
-If you want to read more about proof-of-work, I recommend reading [this whitepaper](https://www.researchgate.net/publication/374638786_Proof-of-Work_CAPTCHA_with_password_cracking_functionality)
+If you want to read more about proof-of-work, I recommend reading [this whitepaper](https://www.researchgate.net/publication/374638786_Proof-of-Work_CAPTCHA_with_password_cracking_functionality)
+
+
+## Why proof-of-work?
+
+Every captcha is solvable by bots or by paid humans. The only question is how to make it costly for bots but invisible for users. Proof-of-work is the perfect balance for this problem.

docs/guide/standalone.md

@@ -33,7 +33,7 @@ Then, you can access the dashboard at `http://localhost:3000`, log in, and creat
 
 ### Client-side
 
-First, add the Cap widget to your website by following the [Cap docs](https://cap.tiagorangel.com/).
+First, add the Cap widget to your website by following [this guide](widget.md).
 
 Then, you need to configure the widget to use your self-hosted Cap Standalone server. To do this, set the widget's API endpoint option to: