diff --git a/lib/nodes/vendor-helpers.js b/lib/nodes/vendor-helpers.js
index <HASH>..<HASH> 100644
--- a/lib/nodes/vendor-helpers.js
+++ b/lib/nodes/vendor-helpers.js
@@ -46,6 +46,10 @@ function normalize(property, value, prefix){
 function normalizeGradient(parts, prefix){
   /* Fix the degrees to the legacy syntax */
   var val = parts[0];
+
+  // when the gradients were unprefixed, the w3c changed the way that the
+  // angle direction is interpreted. see:
+  // http://blogs.msdn.com/b/ie/archive/2012/06/25/unprefixed-css3-gradients-in-ie10.aspx
   if (parts[1]) val += (prefix ? parseFloat((Math.abs(450 - parts[1]) % 360).toFixed(3)) : parts[1]) + 'deg';
 
   /* Fix the directions to the legacy syntax */
added a bit of documentation for vendorize