diff --git a/00_index.md b/00_index.md
index 75547d1..0d11be9 100644
--- a/00_index.md
+++ b/00_index.md
@@ -204,6 +204,12 @@ Script location: `/usr/local/bin/ddns-update.sh` in CT 108. Full credentials map
 
 ---
 
+| Area | Rule |
+|---|---|
+| **WebSupport DNS — duplicate A values** | WebSupport rejects (422) writing an A record whose IP value already exists on *any other record* in the zone, regardless of hostname. You cannot have two A records pointing at the same IP anywhere in the zone. Fix: all subdomains use CNAME → `spendlik.sk`; only the root A record ever holds an IP. |
+| **WebSupport API — PUT silently resets `name`** | A `PUT` to `/v2/service/{id}/dns/record/{recordId}` that omits the `name` field does NOT preserve the existing name — it silently renames the record to the bare zone apex. Always include `name` explicitly in PUT payloads, or avoid partial-field updates. |
+| **WebSupport API — POST `name` is relative** | Creating a record via POST: `name` is relative to the zone, not a full FQDN. Passing `"email.spendlik.sk"` creates `email.spendlik.sk.spendlik.sk`. Use the bare subdomain only (`"email"`, `"*"`, `"git"`). |
+
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