added gnumake/gmake info
diff --git a/docs/install.html b/docs/install.html
index f126097..605b658 100644
--- a/docs/install.html
+++ b/docs/install.html
@@ -234,6 +234,9 @@
 <pre>
 	make
 </pre>
+<p>(on some systems you may need to run <code>gmake</code> or
+<code>gnumake</code> instead)
+</p>
 <p>
 When finished, libGL.so will be in src/.libs/ and libGLU.so will be in
 si-glu/.libs/, etc.