diff --git a/content/base/src/nsGkAtomList.h b/content/base/src/nsGkAtomList.h
index 08ffe7873be..64bdbd3bf14 100644
--- a/content/base/src/nsGkAtomList.h
+++ b/content/base/src/nsGkAtomList.h
@@ -1750,4 +1750,3 @@ GK_ATOM(_moz_windows_classic, "-moz-windows-classic")
 GK_ATOM(_moz_touch_enabled, "-moz-touch-enabled")
 GK_ATOM(_moz_maemo_classic, "-moz-maemo-classic")
 GK_ATOM(_moz_menubar_drag, "-moz-menubar-drag")
-GK_ATOM(_moz_device_pixel_ratio, "-moz-device-pixel-ratio")
diff --git a/layout/style/nsCSSParser.cpp b/layout/style/nsCSSParser.cpp
index 588e9a6d265..4f512fdeed8 100644
--- a/layout/style/nsCSSParser.cpp
+++ b/layout/style/nsCSSParser.cpp
@@ -1791,9 +1791,6 @@ CSSParserImpl::ParseMediaQueryExpression(nsMediaQuery* aQuery)
           expr->mValue.GetIntValue() > 1)
         rv = PR_FALSE;
       break;
-    case nsMediaFeature::eFloat:
-      rv = ParseNonNegativeVariant(expr->mValue, VARIANT_NUMBER, nsnull);
-      break;
     case nsMediaFeature::eIntRatio:
       {
         // Two integers separated by '/', with optional whitespace on
diff --git a/layout/style/nsCSSStyleSheet.cpp b/layout/style/nsCSSStyleSheet.cpp
index 2a755eaaf53..c1f2489b4b6 100644
--- a/layout/style/nsCSSStyleSheet.cpp
+++ b/layout/style/nsCSSStyleSheet.cpp
@@ -249,15 +249,6 @@ nsMediaExpression::Matches(nsPresContext *aPresContext,
         cmp = DoCompare(actual.GetIntValue(), required.GetIntValue());
       }
       break;
-    case nsMediaFeature::eFloat:
-      {
-        NS_ASSERTION(actual.GetUnit() == eCSSUnit_Number,
-                     "bad actual value");
-        NS_ASSERTION(required.GetUnit() == eCSSUnit_Number,
-                     "bad required value");
-        cmp = DoCompare(actual.GetFloatValue(), required.GetFloatValue());
-      }
-      break;
     case nsMediaFeature::eIntRatio:
       {
         NS_ASSERTION(actual.GetUnit() == eCSSUnit_Array &&
@@ -431,15 +422,6 @@ nsMediaQuery::AppendToString(nsAString& aString) const
           // written without anything extra.
           expr.mValue.AppendToString(eCSSProperty_z_index, aString);
           break;
-        case nsMediaFeature::eFloat:
-          {
-            NS_ASSERTION(expr.mValue.GetUnit() == eCSSUnit_Number,
-                         "bad unit");
-            // Use 'line-height' as a property that takes float values
-            // written in the normal way.
-            expr.mValue.AppendToString(eCSSProperty_line_height, aString);
-          }
-          break;
         case nsMediaFeature::eIntRatio:
           {
             NS_ASSERTION(expr.mValue.GetUnit() == eCSSUnit_Array,
diff --git a/layout/style/nsMediaFeatures.cpp b/layout/style/nsMediaFeatures.cpp
index a222b63b306..c88fb187a00 100644
--- a/layout/style/nsMediaFeatures.cpp
+++ b/layout/style/nsMediaFeatures.cpp
@@ -185,6 +185,7 @@ GetDeviceAspectRatio(nsPresContext* aPresContext, const nsMediaFeature*,
     return MakeArray(GetDeviceSize(aPresContext), aResult);
 }
 
+
 static nsresult
 GetColor(nsPresContext* aPresContext, const nsMediaFeature*,
          nsCSSValue& aResult)
@@ -260,15 +261,6 @@ GetGrid(nsPresContext* aPresContext, const nsMediaFeature*,
     return NS_OK;
 }
 
-static nsresult
-GetDevicePixelRatio(nsPresContext* aPresContext, const nsMediaFeature*,
-                    nsCSSValue& aResult)
-{
-  float ratio = aPresContext->CSSPixelsToDevPixels(1.0f);
-  aResult.SetFloatValue(ratio, eCSSUnit_Number);
-  return NS_OK;
-}
-
 static nsresult
 GetSystemMetric(nsPresContext* aPresContext, const nsMediaFeature* aFeature,
                 nsCSSValue& aResult)
@@ -385,13 +377,6 @@ nsMediaFeatures::features[] = {
     },
 
     // Mozilla extensions
-    {
-        &nsGkAtoms::_moz_device_pixel_ratio,
-        nsMediaFeature::eMinMaxAllowed,
-        nsMediaFeature::eFloat,
-        { nsnull },
-        GetDevicePixelRatio
-    },
     {
         &nsGkAtoms::_moz_scrollbar_start_backward,
         nsMediaFeature::eMinMaxNotAllowed,
diff --git a/layout/style/nsMediaFeatures.h b/layout/style/nsMediaFeatures.h
index 8fa7f289215..0cacd230d51 100644
--- a/layout/style/nsMediaFeatures.h
+++ b/layout/style/nsMediaFeatures.h
@@ -63,7 +63,6 @@ struct nsMediaFeature {
         // was given (in addition to the types listed below).
         eLength,     // values are such that nsCSSValue::IsLengthUnit() is true
         eInteger,    // values are eCSSUnit_Integer
-        eFloat,      // values are eCSSUnit_Number
         eBoolInteger,// values are eCSSUnit_Integer (0, -0, or 1 only)
         eIntRatio,   // values are eCSSUnit_Array of two eCSSUnit_Integer
         eResolution, // values are in eCSSUnit_Inch (for dpi) or
diff --git a/layout/style/test/Makefile.in b/layout/style/test/Makefile.in
index 0aa2b945a1b..9815d73d837 100644
--- a/layout/style/test/Makefile.in
+++ b/layout/style/test/Makefile.in
@@ -153,7 +153,6 @@ _TEST_FILES =	test_acid3_test46.html \
 		test_media_queries.html \
 		test_media_queries_dynamic.html \
 		test_media_queries_dynamic_xbl.html \
-		test_moz_device_pixel_ratio.html \
 		test_namespace_rule.html \
 		test_of_type_selectors.xhtml \
 		test_parse_rule.html \
diff --git a/layout/style/test/test_media_queries.html b/layout/style/test/test_media_queries.html
index 5a3dd78430f..c13b3bac9bb 100644
--- a/layout/style/test/test_media_queries.html
+++ b/layout/style/test/test_media_queries.html
@@ -26,13 +26,6 @@ SimpleTest.waitForExplicitFinish();
 
 var iframe;
 
-function getZoomRatio() {
-  netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");
-  var utils = window.QueryInterface(Components.interfaces.nsIInterfaceRequestor)
-                    .getInterface(Components.interfaces.nsIDOMWindowUtils);
-  return utils.screenPixelsPerCSSPixel;
-}
-
 function run() {
   iframe = document.getElementById("subdoc");
   var subdoc = iframe.contentDocument;
@@ -336,26 +329,6 @@ function run() {
   should_apply("not all and (max-device-aspect-ratio: " + low_dar_2 + ")");
   expression_should_not_be_parseable("max-device-aspect-ratio");
 
-  var real_dpr = 1.0 * getZoomRatio();
-  var high_dpr = 1.1 * getZoomRatio();
-  var low_dpr = 0.9 * getZoomRatio();
-  should_apply("all and (max--moz-device-pixel-ratio: " + real_dpr + ")");
-  should_apply("all and (min--moz-device-pixel-ratio: " + real_dpr + ")");
-  should_not_apply("not all and (max--moz-device-pixel-ratio: " + real_dpr + ")");
-  should_not_apply("not all and (min--moz-device-pixel-ratio: " + real_dpr + ")");
-  should_apply("all and (min--moz-device-pixel-ratio: " + low_dpr + ")");
-  should_apply("all and (max--moz-device-pixel-ratio: " + high_dpr + ")");
-  should_not_apply("all and (max--moz-device-pixel-ratio: " + low_dpr + ")");
-  should_not_apply("all and (min--moz-device-pixel-ratio: " + high_dpr + ")");
-  should_apply("not all and (max--moz-device-pixel-ratio: " + low_dpr + ")");
-  should_apply("not all and (min--moz-device-pixel-ratio: " + high_dpr + ")");
-  should_apply("(-moz-device-pixel-ratio: " + real_dpr + ")");
-  should_not_apply("(-moz-device-pixel-ratio: " + high_dpr + ")");
-  should_not_apply("(-moz-device-pixel-ratio: " + low_dpr + ")");
-  should_apply("(-moz-device-pixel-ratio)");
-  expression_should_not_be_parseable("min--moz-device-pixel-ratio");
-  expression_should_not_be_parseable("max--moz-device-pixel-ratio");
-
   features = [ "max-aspect-ratio", "device-aspect-ratio" ];
   for (i in features) {
     feature = features[i];
diff --git a/layout/style/test/test_moz_device_pixel_ratio.html b/layout/style/test/test_moz_device_pixel_ratio.html
deleted file mode 100644
index 24a80950bd6..00000000000
--- a/layout/style/test/test_moz_device_pixel_ratio.html
+++ /dev/null
@@ -1,87 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<!--
-https://bugzilla.mozilla.org/show_bug.cgi?id=474356
--->
-<head>
-  <title>Test for Bug 474356</title>
-  <script type="text/javascript" src="/MochiKit/packed.js"></script>
-  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
-  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
-  <style>.zoom-test { visibility: hidden; }</style>
-  <style><!-- placeholder for dynamic additions --></style>
-</head>
-<body onload="run()">
-<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=474356">Mozilla Bug 474356</a>
-<div id="content" style="display: none">
-  
-</div>
-<script type="text/javascript">
-</script>
-<pre id="test">
-<div id="zoom1" class="zoom-test"></div>
-<div id="zoom2" class="zoom-test"></div>
-<div id="zoom3" class="zoom-test"></div>
-<script class="testbody" type="application/javascript">
-
-/** Test for Bug 474356 **/
-
-SimpleTest.waitForExplicitFinish();
-
-function run() {
-  netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");
-  viewer = window.QueryInterface(Components.interfaces.nsIInterfaceRequestor)
-                 .getInterface(Components.interfaces.nsIWebNavigation)
-                 .QueryInterface(Components.interfaces.nsIDocShell)
-                 .contentViewer
-                 .QueryInterface(Components.interfaces.nsIMarkupDocumentViewer);
-
-
-  function zoom(factor) {
-    netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");
-    viewer.fullZoom = factor;
-  }
-
-  function isVisible(divName) {
-    return window.getComputedStyle(document.getElementById(divName), null).visibility == "visible";
-  }
-
-  function getZoomRatio() {
-    netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");
-    var utils = window.QueryInterface(Components.interfaces.nsIInterfaceRequestor)
-                      .getInterface(Components.interfaces.nsIDOMWindowUtils);
-    return utils ? utils.screenPixelsPerCSSPixel : 1.0;
-  }
-
-  var screenPixelsPerCSSPixel = getZoomRatio();
-  var baseRatio = 1.0 * screenPixelsPerCSSPixel;
-  var doubleRatio = 2.0 * screenPixelsPerCSSPixel;
-  var halfRatio = 0.5 * screenPixelsPerCSSPixel;
-  var styleElem = document.getElementsByTagName("style")[1];
-  styleElem.textContent = 
-      ["@media all and (-moz-device-pixel-ratio: " + baseRatio + ") {",
-         "#zoom1 { visibility: visible; }",
-       "}",
-       "@media all and (-moz-device-pixel-ratio: " + doubleRatio + ") {",
-         "#zoom2 { visibility: visible; }",
-       "}",
-       "@media all and (-moz-device-pixel-ratio: " + halfRatio + ") {",
-         "#zoom3 { visibility: visible; }",
-       "}"
-      ].join("\n");
-
-  ok(isVisible("zoom1"), "Base ratio rule should apply at base zoom level");
-  ok(!isVisible("zoom2") && !isVisible("zoom3"), "no other rules should apply");
-  zoom(2 * screenPixelsPerCSSPixel);
-  ok(isVisible("zoom2"), "Double ratio rule should apply at double zoom level");
-  ok(!isVisible("zoom1") && !isVisible("zoom3"), "no other rules should apply");
-  zoom(0.5 * screenPixelsPerCSSPixel);
-  ok(isVisible("zoom3"), "Half ratio rule should apply at half zoom level");
-  ok(!isVisible("zoom1") && !isVisible("zoom2"), "no other rules should apply");
-
-  SimpleTest.finish();
-}
-</script>
-</pre>
-</body>
-</html>