diff --git a/doc/src/man/linkcheckerrc.rst b/doc/src/man/linkcheckerrc.rst
index 0b31a958..d7ee4382 100644
--- a/doc/src/man/linkcheckerrc.rst
+++ b/doc/src/man/linkcheckerrc.rst
@@ -534,8 +534,10 @@ warnings.
 HtmlSyntaxCheck
 ^^^^^^^^^^^^^^^
 
-Check the syntax of HTML pages with the online W3C HTML validator. See
-https://validator.w3.org/docs/api.html.
+Check the syntax of HTML pages by submitting their URLs to the online W3C HTML
+validator. If a page URL is not accessible to the validator no check is
+performed and no warning given.
+See https://validator.w3.org/docs/api.html.
 
 .. note::
 
@@ -553,8 +555,10 @@ Print HTTP headers in URL info.
 CssSyntaxCheck
 ^^^^^^^^^^^^^^
 
-Check the syntax of HTML pages with the online W3C CSS validator. See
-https://jigsaw.w3.org/css-validator/manual.html#expert.
+Check the syntax of CSS stylesheets by submitting their URLs to the online W3C CSS
+validator. If a stylesheet URL is not accessible to the validator no check is
+performed and no warning given.
+See https://jigsaw.w3.org/css-validator/manual.html#expert.
 
 VirusCheck
 ^^^^^^^^^^
diff --git a/linkcheck/plugins/syntaxchecks.py b/linkcheck/plugins/syntaxchecks.py
index a011d6a1..2dd13026 100644
--- a/linkcheck/plugins/syntaxchecks.py
+++ b/linkcheck/plugins/syntaxchecks.py
@@ -83,7 +83,7 @@ class HtmlSyntaxCheck(_ContentPlugin):
 
 
 class CssSyntaxCheck(_ContentPlugin):
-    """Check the syntax of HTML pages with the online W3C CSS validator.
+    """Check the syntax of CSS stylesheets with the online W3C CSS validator.
     See https://jigsaw.w3.org/css-validator/manual.html#expert.
     """