--- a/browser/themes/linux/devtools/ruleview.css
+++ b/browser/themes/linux/devtools/ruleview.css
@@ -23,20 +23,26 @@
   margin-top: 4px;
   -moz-user-select: none;
 }
 
 .ruleview-rule-source:hover {
   text-decoration: underline;
 }
 
-.ruleview-rule {
+.ruleview-rule,
+#noResults {
   padding: 2px 4px;
 }
 
+#noResults {
+  font: message-box;
+  color: GrayText;
+}
+
 .ruleview-rule + .ruleview-rule {
   border-top-width: 1px;
   border-top-style: dotted;
 }
 
 .ruleview-warning {
   background: url("chrome://browser/skin/devtools/alerticon-warning.png");
   -moz-margin-start: 5px;

--- a/browser/themes/osx/devtools/ruleview.css
+++ b/browser/themes/osx/devtools/ruleview.css
@@ -23,20 +23,26 @@
   margin-top: 4px;
   -moz-user-select: none;
 }
 
 .ruleview-rule-source:hover {
   text-decoration: underline;
 }
 
-.ruleview-rule {
+.ruleview-rule,
+#noResults {
   padding: 2px 4px;
 }
 
+#noResults {
+  font: message-box;
+  color: GrayText;
+}
+
 .ruleview-rule + .ruleview-rule {
   border-top-width: 1px;
   border-top-style: dotted;
 }
 
 .ruleview-warning {
   background: url("chrome://browser/skin/devtools/alerticon-warning.png");
   -moz-margin-start: 5px;

--- a/browser/themes/windows/devtools/ruleview.css
+++ b/browser/themes/windows/devtools/ruleview.css
@@ -23,20 +23,26 @@
   margin-top: 4px;
   -moz-user-select: none;
 }
 
 .ruleview-rule-source:hover {
   text-decoration: underline;
 }
 
-.ruleview-rule {
+.ruleview-rule,
+#noResults {
   padding: 2px 4px;
 }
 
+#noResults {
+  font: message-box;
+  color: GrayText;
+}
+
 .ruleview-rule + .ruleview-rule {
   border-top-width: 1px;
   border-top-style: dotted;
 }
 
 .ruleview-warning {
   background: url("chrome://browser/skin/devtools/alerticon-warning.png");
   -moz-margin-start: 5px;