Index: lib/elemHide.js
===================================================================
--- a/lib/elemHide.js
+++ b/lib/elemHide.js
@@ -59,6 +59,12 @@
 let styleURL = null;
 
 /**
+ * Lookup table, blocking filters by domain which they are applied to
+ * @type Object
+ */
+let filtersByDomain = Object.create(null);
+
+/**
  * Element hiding component
  * @class
  */
@@ -105,6 +111,7 @@
     keyByFilter = Object.create(null);
     knownExceptions = Object.create(null);
     exceptions = Object.create(null);
+    filtersByDomain = Object.create(null);
     ElemHide.isDirty = false;
     ElemHide.unapply();
   },
@@ -131,6 +138,28 @@
       if (filter.text in keyByFilter)
         return;
 
+      if (!("nsIStyleSheetService" in Ci))
+      {
+        let domains = filter.domains;
+        if (domains === null)
+        {
+          domains = Object.create(null);
+          domains[""] = undefined;
+        }
+
+        for (let domain in domains)
+        {
+          if (!(domain in filtersByDomain))
+          {
+            filtersByDomain[domain] = Object.create(null);
+            filtersByDomain[domain]._length = 0;
+          }
+
+          filtersByDomain[domain][filter.text] = filter.isActiveOnDomain(domain);
+          filtersByDomain[domain]._length++;
+        }
+      }
+
       let key;
       do {
         key = Math.random().toFixed(15).substr(5);
@@ -164,6 +193,26 @@
       if (!(filter.text in keyByFilter))
         return;
 
+      if (!("nsIStyleSheetService" in Ci))
+      {
+        let domains = filter.domains;
+        if (!domains)
+        {
+          domains = Object.create(null);
+          domains[""] = undefined;
+        }
+
+        for (let domain in domains)
+        {
+          if (domain in filtersByDomain && filter.text in filtersByDomain[domain])
+          {
+            delete filtersByDomain[domain][filter.text];
+            if (!--filtersByDomain[domain]._length)
+              delete filtersByDomain[domain];
+          }
+        }
+      }
+
       let key = keyByFilter[filter.text];
       delete filterByKey[key];
       delete keyByFilter[filter.text];
@@ -377,16 +426,59 @@
    */
   getSelectorsForDomain: function(/**String*/ domain, /**Boolean*/ specificOnly)
   {
-    let result = [];
-    for (let key in filterByKey)
+    let selectors = [];
+    domain = domain.toUpperCase();
+
+    if (!specificOnly)
     {
-      let filter = filterByKey[key];
-      if (specificOnly && (!filter.domains || filter.domains[""]))
-        continue;
+      let filterTexts = filtersByDomain[""];
+      if (filterTexts)
+      {
+        for (let filterText in filterTexts)
+        {
+          if (filterTexts[filterText])
+          {
+            let filter = filterByKey[keyByFilter[filterText]];
+            if (!filter)
+              continue;
+            
+            let selector = filter.selector;
+            if (filter.isActiveOnDomain(docDomain) && !this.getException(selector, docDomain))
+              selectors[selectors.length] = selector;
+          }
+        }
+      }
+    }
 
-      if (filter.isActiveOnDomain(domain) && !this.getException(filter, domain))
-        result.push(filter.selector);
+    while (true)
+    {
+      if (domain && domain in filtersByDomain)
+      {
+        let filterTexts = filtersByDomain[domain];
+        if (filterTexts)
+        {
+          for (let filterText in filterTexts)
+          {
+            if (filterTexts[filterText])
+            {
+              let filter = filterByKey[keyByFilter[filterText]];
+              if (!filter)
+                continue;
+              
+              let selector = filter.selector;
+              if (!this.getException(selector, docDomain))
+                selectors[selectors.length] = selector;
+            }
+          }
+        }
+      }
+
+      let nextDot = domain.indexOf(".");
+      if (nextDot < 0)
+        break;
+      domain = domain.substr(nextDot + 1);
     }
-    return result;
+
+    return selectors;
   }
 };