diff --git a/src/css/support.js b/src/css/support.js
index 0be4f6392..da9ee34f1 100644
--- a/src/css/support.js
+++ b/src/css/support.js
@@ -8,6 +8,7 @@ define([
 		pixelPositionVal,
 		div = document.createElement( "div" ),
 		containerStyles = "border:0;width:0;height:0;position:absolute;top:0;left:-9999px",
+		// Support: Firefox<29, Android 2.3 (Prefixed box-sizing versions).
 		divReset =
 			"-webkit-box-sizing:content-box;-moz-box-sizing:content-box;box-sizing:content-box;" +
 			"display:block;padding:0;margin:0;border:0";
@@ -162,6 +163,7 @@ define([
 
 		body.appendChild( container ).appendChild( div );
 
+		// Support: Firefox<29, Android 2.3 (Prefixed box-sizing versions).
 		div.style.cssText =
 			"-webkit-box-sizing:border-box;-moz-box-sizing:border-box;box-sizing:border-box;" +
 				"position:absolute;display:block;padding:1px;border:1px;width:4px;" +
diff --git a/src/effects/support.js b/src/effects/support.js
index 2391bcbff..85b77c9cc 100644
--- a/src/effects/support.js
+++ b/src/effects/support.js
@@ -6,6 +6,7 @@ define([
 (function() {
 	var a, shrinkWrapBlocksVal,
 		div = document.createElement( "div" ),
+		// Support: Firefox<29, Android 2.3 (Prefixed box-sizing versions).
 		divReset =
 			"-webkit-box-sizing:content-box;-moz-box-sizing:content-box;box-sizing:content-box;" +
 			"display:block;padding:0;margin:0;border:0";
diff --git a/test/unit/css.js b/test/unit/css.js
index 0822fc68b..f401ec7e3 100644
--- a/test/unit/css.js
+++ b/test/unit/css.js
@@ -847,6 +847,7 @@ test("Do not append px (#9548, #12990)", function() {
 test("css('width') and css('height') should respect box-sizing, see #11004", function() {
 	expect( 4 );
 
+	// Support: Firefox<29, Android 2.3 (Prefixed box-sizing versions).
 	var el_dis = jQuery("<div style='width:300px;height:300px;margin:2px;padding:2px;-moz-box-sizing:border-box;-webkit-box-sizing:border-box;box-sizing:border-box;'>test</div>"),
 		el = el_dis.clone().appendTo("#qunit-fixture");
 
diff --git a/test/unit/dimensions.js b/test/unit/dimensions.js
index c6165b0f9..97e23d7e2 100644
--- a/test/unit/dimensions.js
+++ b/test/unit/dimensions.js
@@ -418,6 +418,7 @@ test( "getters on non elements should return null", function() {
 test("setters with and without box-sizing:border-box", function(){
 	expect(20);
 
+	// Support: Firefox<29, Android 2.3 (Prefixed box-sizing versions).
 	var el_bb = jQuery("<div style='width:114px;height:114px;margin:5px;padding:3px;border:4px solid white;-moz-box-sizing:border-box;-webkit-box-sizing:border-box;box-sizing:border-box;'>test</div>").appendTo("#qunit-fixture"),
 		el = jQuery("<div style='width:100px;height:100px;margin:5px;padding:3px;border:4px solid white;'>test</div>").appendTo("#qunit-fixture"),
 		expected = 100;