diff --git a/src/selector.js b/src/selector.js
index fcab67fb..32f48c41 100644
--- a/src/selector.js
+++ b/src/selector.js
@@ -8,7 +8,8 @@
 
 var chunker = /((?:\((?:\([^()]+\)|[^()]+)+\)|\[(?:\[[^[\]]*\]|['"][^'"]*['"]|[^[\]'"]+)+\]|\\.|[^ >+~,(\[\\]+)+|[>+~])(\s*,\s*)?/g,
 	done = 0,
-	toString = Object.prototype.toString;
+	toString = Object.prototype.toString,
+	hasDuplicate = false;
 
 var Sizzle = function(selector, context, results, seed) {
 	results = results || [];
@@ -17,19 +18,19 @@ var Sizzle = function(selector, context, results, seed) {
 	if ( context.nodeType !== 1 && context.nodeType !== 9 ) {
 		return [];
 	}
-
+	
 	if ( !selector || typeof selector !== "string" ) {
 		return results;
 	}
 
 	var parts = [], m, set, checkSet, check, mode, extra, prune = true, contextXML = isXML(context);
-
+	
 	// Reset the position of the chunker regexp (start from head)
 	chunker.lastIndex = 0;
-
+	
 	while ( (m = chunker.exec(selector)) !== null ) {
 		parts.push( m[1] );
-
+		
 		if ( m[2] ) {
 			extra = RegExp.rightContext;
 			break;
@@ -158,7 +159,7 @@ Sizzle.find = function(expr, context, isXML){
 
 	for ( var i = 0, l = Expr.order.length; i < l; i++ ) {
 		var type = Expr.order[i], match;
-
+		
 		if ( (match = Expr.match[ type ].exec( expr )) ) {
 			var left = RegExp.leftContext;
 
@@ -420,7 +421,7 @@ var Expr = Sizzle.selectors = {
 		},
 		ATTR: function(match, curLoop, inplace, result, not, isXML){
 			var name = match[1].replace(/\\/g, "");
-
+			
 			if ( !isXML && Expr.attrMap[name] ) {
 				match[1] = Expr.attrMap[name];
 			}
@@ -446,7 +447,7 @@ var Expr = Sizzle.selectors = {
 			} else if ( Expr.match.POS.test( match[0] ) || Expr.match.CHILD.test( match[0] ) ) {
 				return true;
 			}
-
+			
 			return match;
 		},
 		POS: function(match){
@@ -580,20 +581,20 @@ var Expr = Sizzle.selectors = {
 					if ( first == 1 && last == 0 ) {
 						return true;
 					}
-
+					
 					var doneName = match[0],
 						parent = elem.parentNode;
-
+	
 					if ( parent && (parent.sizcache !== doneName || !elem.nodeIndex) ) {
 						var count = 0;
 						for ( node = parent.firstChild; node; node = node.nextSibling ) {
 							if ( node.nodeType === 1 ) {
 								node.nodeIndex = ++count;
 							}
-						}
+						} 
 						parent.sizcache = doneName;
 					}
-
+					
 					var diff = elem.nodeIndex - last;
 					if ( first == 0 ) {
 						return diff == 0;
@@ -666,7 +667,7 @@ var makeArray = function(array, results) {
 		results.push.apply( results, array );
 		return results;
 	}
-
+	
 	return array;
 };
 
@@ -760,6 +761,7 @@ if ( document.documentElement.compareDocumentPosition ) {
 	}
 
 	root.removeChild( form );
+	root = form = null; // release memory in IE
 })();
 
 (function(){
@@ -800,6 +802,8 @@ if ( document.documentElement.compareDocumentPosition ) {
 			return elem.getAttribute("href", 2);
 		};
 	}
+
+	div = null; // release memory in IE
 })();
 
 if ( document.querySelectorAll ) (function(){
@@ -811,7 +815,7 @@ if ( document.querySelectorAll ) (function(){
 	if ( div.querySelectorAll && div.querySelectorAll(".TEST").length === 0 ) {
 		return;
 	}
-
+	
 	Sizzle = function(query, context, extra, seed){
 		context = context || document;
 
@@ -822,13 +826,15 @@ if ( document.querySelectorAll ) (function(){
 				return makeArray( context.querySelectorAll(query), extra );
 			} catch(e){}
 		}
-
+		
 		return oldSizzle(query, context, extra, seed);
 	};
 
 	for ( var prop in oldSizzle ) {
 		Sizzle[ prop ] = oldSizzle[ prop ];
 	}
+
+	div = null; // release memory in IE
 })();
 
 if ( document.getElementsByClassName && document.documentElement.getElementsByClassName ) (function(){
@@ -851,6 +857,8 @@ if ( document.getElementsByClassName && document.documentElement.getElementsByCl
 			return context.getElementsByClassName(match[1]);
 		}
 	};
+
+	div = null; // release memory in IE
 })();
 
 function dirNodeCheck( dir, cur, doneName, checkSet, nodeCheck, isXML ) {
@@ -969,7 +977,7 @@ jQuery.expr = Sizzle.selectors;
 jQuery.expr[":"] = jQuery.expr.filters;
 
 Sizzle.selectors.filters.hidden = function(elem){
-	return elem.offsetWidth === 0 && elem.offsetHeight === 0;
+	return elem.offsetWidth === 0 || elem.offsetHeight === 0;
 };
 
 Sizzle.selectors.filters.visible = function(elem){