Adds comments related to the public RPC endpoints (#22797)

* Adds comments related to the public RPC endpoints

* Update docs/src/cluster/rpc-endpoints.md

Co-authored-by: Michael Vines <mvines@gmail.com>

Co-authored-by: Brian Long <bl@triton.one>
Co-authored-by: Tyera Eulberg <teulberg@gmail.com>
Co-authored-by: Michael Vines <mvines@gmail.com>

docs/src/cluster/rpc-endpoints.md

@@ -36,7 +36,7 @@ public RPC endpoints currently available and recommended for each public cluster
 
 ## Mainnet Beta
 
-#### Endpoints
+#### Endpoints*
 
 - `https://api.mainnet-beta.solana.com` - Solana-hosted api node cluster, backed by a load balancer; rate-limited
 - `https://solana-api.projectserum.com` - Project Serum-hosted api node
@@ -48,3 +48,17 @@ public RPC endpoints currently available and recommended for each public cluster
 - Maximum concurrent connections per IP: 40
 - Maximum connection rate per 10 seconds per IP: 40
 - Maximum amount of data per 30 second: 100 MB
+
+*The public RPC endpoints are not intended for production applications. Please
+use dedicated/private RPC servers when you launch your application, drop NFTs,
+etc. The public services are subject to abuse and rate limits may change
+without prior notice. Likewise, high-traffic websites may be blocked without
+prior notice.
+
+## Common HTTP Error Codes
+
+- 403 -- Your IP address or website has been blocked. It is time to run your own RPC server(s) or find a private service.
+- 429 -- Your IP address is exceeding the rate limits. Slow down! Use the
+[Retry-After](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Retry-After)
+HTTP response header to determine how long to wait before making another
+request.