diff --git a/layout/style/CSSStyleSheet.cpp b/layout/style/CSSStyleSheet.cpp
index 05bb84018f..f2f89b9127 100644
--- a/layout/style/CSSStyleSheet.cpp
+++ b/layout/style/CSSStyleSheet.cpp
@@ -283,6 +283,10 @@ nsMediaExpression::Matches(nsPresContext *aPresContext,
       return cmp != 1;
     case nsMediaExpression::eEqual:
       return cmp == 0;
+    case nsMediaExpression::eMinExclusive:
+      return cmp == 1;
+    case nsMediaExpression::eMaxExclusive:
+      return cmp == -1;
   }
   NS_NOTREACHED("unexpected mRange");
   return false;
@@ -487,7 +491,13 @@ nsMediaQuery::AppendToString(nsAString& aString) const
     aString.Append(nsDependentAtomString(*feature->mName));
 
     if (expr.mValue.GetUnit() != eCSSUnit_Null) {
-      aString.AppendLiteral(": ");
+      if (expr.mRange == nsMediaExpression::eMinExclusive) {
+        aString.AppendLiteral(" > ");
+      } else if (expr.mRange == nsMediaExpression::eMaxExclusive) {
+        aString.AppendLiteral(" < ");
+      } else {
+        aString.AppendLiteral(": ");
+      }
       switch (feature->mValueType) {
         case nsMediaFeature::eLength:
           NS_ASSERTION(expr.mValue.IsLengthUnit(), "bad unit");
diff --git a/layout/style/nsCSSParser.cpp b/layout/style/nsCSSParser.cpp
index 59872b0f67..afb9f195a8 100644
--- a/layout/style/nsCSSParser.cpp
+++ b/layout/style/nsCSSParser.cpp
@@ -3845,9 +3845,7 @@ CSSParserImpl::ParseMediaQueryExpression(nsMediaQuery* aQuery)
       break;
     }
   }
-  if (!feature->mName ||
-      (expr->mRange != nsMediaExpression::eEqual &&
-       feature->mRangeType != nsMediaFeature::eMinMaxAllowed)) {
+  if (!feature->mName) {
     REPORT_UNEXPECTED_TOKEN(PEMQExpectedFeatureName);
     SkipUntil(')');
     return false;
@@ -3865,13 +3863,52 @@ CSSParserImpl::ParseMediaQueryExpression(nsMediaQuery* aQuery)
     return true;
   }
 
-  if (!mToken.IsSymbol(':')) {
+  bool usesRangeSyntax = false;
+  if (mToken.IsSymbol('<') || mToken.IsSymbol('>') || mToken.IsSymbol('=')) {
+    if (expr->mRange != nsMediaExpression::eEqual) {
+      REPORT_UNEXPECTED_TOKEN(PEMQExpectedFeatureNameEnd);
+      UngetToken();
+      SkipUntil(')');
+      return false;
+    }
+
+    usesRangeSyntax = true;
+    char16_t rangeSymbol = mToken.mSymbol;
+    bool inclusive = rangeSymbol == '=';
+
+    if (rangeSymbol != '=') {
+      if (!GetToken(true)) {
+        REPORT_UNEXPECTED_EOF(PEMQExpressionEOF);
+        return false;
+      }
+      if (mToken.IsSymbol('=')) {
+        inclusive = true;
+      } else {
+        UngetToken();
+      }
+    }
+
+    if (rangeSymbol == '>') {
+      expr->mRange = inclusive ? nsMediaExpression::eMin
+                               : nsMediaExpression::eMinExclusive;
+    } else if (rangeSymbol == '<') {
+      expr->mRange = inclusive ? nsMediaExpression::eMax
+                               : nsMediaExpression::eMaxExclusive;
+    }
+  } else if (!mToken.IsSymbol(':')) {
     REPORT_UNEXPECTED_TOKEN(PEMQExpectedFeatureNameEnd);
     UngetToken();
     SkipUntil(')');
     return false;
   }
 
+  if ((expr->mRange != nsMediaExpression::eEqual || usesRangeSyntax) &&
+      feature->mRangeType != nsMediaFeature::eMinMaxAllowed) {
+    REPORT_UNEXPECTED_TOKEN(PEMQExpectedFeatureName);
+    SkipUntil(')');
+    return false;
+  }
+
   bool rv = false;
   switch (feature->mValueType) {
     case nsMediaFeature::eLength:
diff --git a/layout/style/nsIMediaList.h b/layout/style/nsIMediaList.h
index 8f8c692cd6..52244b48f4 100644
--- a/layout/style/nsIMediaList.h
+++ b/layout/style/nsIMediaList.h
@@ -33,7 +33,7 @@ class DocumentRule;
 } // namespace mozilla
 
 struct nsMediaExpression {
-  enum Range { eMin, eMax, eEqual };
+  enum Range { eMin, eMax, eEqual, eMinExclusive, eMaxExclusive };
 
   const nsMediaFeature *mFeature;
   Range mRange;
diff --git a/layout/style/test/test_media_queries.html b/layout/style/test/test_media_queries.html
index a962215d34..90b55a2ac5 100644
--- a/layout/style/test/test_media_queries.html
+++ b/layout/style/test/test_media_queries.html
@@ -290,6 +290,12 @@ function run() {
     should_apply("all and (max-" + feature + ": " + value + "px)");
     should_apply("all and (max-" + feature + ": " + (value + 1) + "px)");
     should_not_apply("all and (max-" + feature + ": " + (value - 1) + "px)");
+    should_apply("all and (" + feature + " >= " + value + "px)");
+    should_not_apply("all and (" + feature + " > " + value + "px)");
+    should_apply("all and (" + feature + " > " + (value - 1) + "px)");
+    should_apply("all and (" + feature + " <= " + value + "px)");
+    should_not_apply("all and (" + feature + " < " + value + "px)");
+    should_apply("all and (" + feature + " < " + (value + 1) + "px)");
     should_not_apply("all and (min-" + feature + ": " +
                      (Math.ceil(value/em_size) + 1) + "em)");
     should_apply("all and (min-" + feature + ": " +
@@ -349,6 +355,9 @@ function run() {
   should_apply("(orientation: landscape)");
   should_not_apply("(orientation: portrait)");
   should_apply("not all and (orientation: portrait)");
+  expression_should_not_be_parseable("orientation > landscape");
+  expression_should_not_be_parseable("min-width > 1px");
+  expression_should_not_be_parseable("width >");
   // ratio that reduces to 59/80
   change_state(function() {
     iframe_style.height = "320px";