document GLSL float f/F suffix bug
diff --git a/docs/shading.html b/docs/shading.html
index 0e1a5e1..0a9f5f3 100644
--- a/docs/shading.html
+++ b/docs/shading.html
@@ -48,6 +48,7 @@
 <li>The inverse trig functions asin(), acos(), and atan() are not implemented
 <li>The gl_Color and gl_SecondaryColor varying vars are interpolated
     without perspective correction
+<li>Floating point literal suffixes 'f' and 'F' aren't allowed.
 </ul>
 
 <p>