--- a/toolkit/components/reader/Readability.js
+++ b/toolkit/components/reader/Readability.js
@@ -103,28 +103,31 @@ Readability.prototype = {
   // The number of top candidates to consider when analysing how
   // tight the competition is among candidates.
   DEFAULT_N_TOP_CANDIDATES: 5,
 
   // The maximum number of pages to loop through before we call
   // it quits and just show a link.
   DEFAULT_MAX_PAGES: 5,
 
+  // Element tags to score by default.
+  DEFAULT_TAGS_TO_SCORE: ["SECTION", "P", "TD", "PRE"],
+
   // All of the regular expressions in use within readability.
   // Defined up here so we don't instantiate them repeatedly in loops.
   REGEXPS: {
     unlikelyCandidates: /banner|combx|comment|community|disqus|extra|foot|header|menu|remark|rss|share|shoutbox|sidebar|skyscraper|sponsor|ad-break|agegate|pagination|pager|popup/i,
     okMaybeItsACandidate: /and|article|body|column|main|shadow/i,
     positive: /article|body|content|entry|hentry|main|page|pagination|post|text|blog|story/i,
     negative: /hidden|banner|combx|comment|com-|contact|foot|footer|footnote|masthead|media|meta|outbrain|promo|related|scroll|share|shoutbox|sidebar|skyscraper|sponsor|shopping|tags|tool|widget/i,
     extraneous: /print|archive|comment|discuss|e[\-]?mail|share|reply|all|login|sign|single|utility/i,
     byline: /byline|author|dateline|writtenby/i,
     replaceFonts: /<(\/?)font[^>]*>/gi,
     normalize: /\s{2,}/g,
-    videos: /https?:\/\/(www\.)?(youtube|youtube-nocookie|player\.vimeo)\.com/i,
+    videos: /https?:\/\/(www\.)?(dailymotion|youtube|youtube-nocookie|player\.vimeo)\.com/i,
     nextLink: /(next|weiter|continue|>([^\|]|$)|»([^\|]|$))/i,
     prevLink: /(prev|earl|old|new|<|«)/i,
     whitespace: /^\s*$/,
     hasContent: /\S$/,
   },
 
   DIV_TO_P_ELEMS: [ "A", "BLOCKQUOTE", "DL", "DIV", "IMG", "OL", "P", "PRE", "TABLE", "UL", "SELECT" ],
 
@@ -181,16 +184,25 @@ Readability.prototype = {
     var slice = Array.prototype.slice;
     var args = slice.call(arguments);
     var nodeLists = args.map(function(list) {
       return slice.call(list);
     });
     return Array.prototype.concat.apply([], nodeLists);
   },
 
+  _getAllNodesWithTag: function(node, tagNames) {
+    if (node.querySelectorAll) {
+      return node.querySelectorAll(tagNames.join(','));
+    }
+    return [].concat.apply([], tagNames.map(function(tag) {
+      return node.getElementsByTagName(tag);
+    }));
+  },
+
   /**
    * Converts each <a> and <img> uri in the given element to an absolute URI.
    *
    * @param Element
    * @return void
    */
   _fixRelativeUris: function(articleContent) {
     var scheme = this._uri.scheme;
@@ -581,16 +593,28 @@ Readability.prototype = {
     if ((rel === "author" || this.REGEXPS.byline.test(matchString)) && this._isValidByline(node.textContent)) {
       this._articleByline = node.textContent.trim();
       return true;
     }
 
     return false;
   },
 
+  _getNodeAncestors: function(node, maxDepth) {
+    maxDepth = maxDepth || 0;
+    var i = 0, ancestors = [];
+    while (node.parentNode) {
+      ancestors.push(node.parentNode)
+      if (maxDepth && ++i === maxDepth)
+        break;
+      node = node.parentNode;
+    }
+    return ancestors;
+  },
+
   /***
    * grabArticle - Using a variety of metrics (content score, classname, element types), find the content that is
    *         most likely to be the stuff a user wants to read. Then return it wrapped up in a div.
    *
    * @param page a document to run upon. Needs to be a full document, complete with body.
    * @return Element
   **/
   _grabArticle: function (page) {
@@ -635,18 +659,19 @@ Readability.prototype = {
               node.tagName !== "BODY" &&
               node.tagName !== "A") {
             this.log("Removing unlikely candidate - " + matchString);
             node = this._removeAndGetNext(node);
             continue;
           }
         }
 
-        if (node.tagName === "P" || node.tagName === "TD" || node.tagName === "PRE")
+        if (this.DEFAULT_TAGS_TO_SCORE.indexOf(node.tagName) !== -1) {
           elementsToScore.push(node);
+        }
 
         // Turn all divs that don't have children block level elements into p's
         if (node.tagName === "DIV") {
           // Sites like http://mobile.slate.com encloses each paragraph with a DIV
           // element. DIVs with only a P element inside and no text content can be
           // safely converted into plain P elements to avoid confusing the scoring
           // algorithm with DIVs with are, in practice, paragraphs.
           if (this._hasSinglePInsideElement(node)) {
@@ -675,57 +700,52 @@ Readability.prototype = {
       /**
        * Loop through all paragraphs, and assign a score to them based on how content-y they look.
        * Then add their score to their parent node.
        *
        * A score is determined by things like number of commas, class names, etc. Maybe eventually link density.
       **/
       var candidates = [];
       this._forEachNode(elementsToScore, function(elementToScore) {
-        var parentNode = elementToScore.parentNode;
-        var grandParentNode = parentNode ? parentNode.parentNode : null;
-        var innerText = this._getInnerText(elementToScore);
-
-        if (!parentNode || typeof(parentNode.tagName) === 'undefined')
+        if (!elementToScore.parentNode || typeof(elementToScore.parentNode.tagName) === 'undefined')
           return;
 
         // If this paragraph is less than 25 characters, don't even count it.
+        var innerText = this._getInnerText(elementToScore);
         if (innerText.length < 25)
           return;
 
-        // Initialize readability data for the parent.
-        if (typeof parentNode.readability === 'undefined') {
-          this._initializeNode(parentNode);
-          candidates.push(parentNode);
-        }
-
-        // Initialize readability data for the grandparent.
-        if (grandParentNode &&
-          typeof(grandParentNode.readability) === 'undefined' &&
-          typeof(grandParentNode.tagName) !== 'undefined') {
-          this._initializeNode(grandParentNode);
-          candidates.push(grandParentNode);
-        }
+        // Exclude nodes with no ancestor.
+        var ancestors = this._getNodeAncestors(elementToScore, 3);
+        if (ancestors.length === 0)
+          return;
 
         var contentScore = 0;
 
         // Add a point for the paragraph itself as a base.
         contentScore += 1;
 
         // Add points for any commas within this paragraph.
         contentScore += innerText.split(',').length;
 
         // For every 100 characters in this paragraph, add another point. Up to 3 points.
         contentScore += Math.min(Math.floor(innerText.length / 100), 3);
 
-        // Add the score to the parent. The grandparent gets half.
-        parentNode.readability.contentScore += contentScore;
+        // Initialize and score ancestors.
+        this._forEachNode(ancestors, function(ancestor, level) {
+          if (!ancestor.tagName)
+            return;
 
-        if (grandParentNode)
-          grandParentNode.readability.contentScore += contentScore / 2;
+          if (typeof(ancestor.readability) === 'undefined') {
+            this._initializeNode(ancestor);
+            candidates.push(ancestor);
+          }
+
+          ancestor.readability.contentScore += contentScore / (level === 0 ? 1 : level * 2);
+        });
       });
 
       // After we've calculated scores, loop through all of the possible
       // candidate nodes we found and find the one with the highest score.
       var topCandidates = [];
       for (var c = 0, cl = candidates.length; c < cl; c += 1) {
         var candidate = candidates[c];
 
@@ -843,20 +863,16 @@ Readability.prototype = {
           if (this.ALTER_TO_DIV_EXCEPTIONS.indexOf(sibling.nodeName) === -1) {
             // We have a node that isn't a common block level element, like a form or td tag.
             // Turn it into a div so it doesn't get filtered out later by accident.
             this.log("Altering sibling:", sibling, 'to div.');
 
             sibling = this._setNodeTag(sibling, "DIV");
           }
 
-          // To ensure a node does not interfere with readability styles,
-          // remove its classnames.
-          sibling.removeAttribute("class");
-
           articleContent.appendChild(sibling);
           // siblings is a reference to the children array, and
           // sibling is removed from the array when we call appendChild().
           // As a result, we must revisit this index since the nodes
           // have been shifted.
           s -= 1;
           sl -= 1;
         }
@@ -948,17 +964,17 @@ Readability.prototype = {
     // Match Facebook's Open Graph title & description properties.
     var propertyPattern = /^\s*og\s*:\s*(description|title)\s*$/gi;
 
     // Find description tags.
     this._forEachNode(metaElements, function(element) {
       var elementName = element.getAttribute("name");
       var elementProperty = element.getAttribute("property");
 
-      if (elementName === "author") {
+      if ([elementName, elementProperty].indexOf("author") !== -1) {
         metadata.byline = element.getAttribute("content");
         return;
       }
 
       var name = null;
       if (namePattern.test(elementName)) {
         name = elementName;
       } else if (propertyPattern.test(elementProperty)) {
@@ -1592,16 +1608,17 @@ Readability.prototype = {
    * @return void
    **/
   _cleanConditionally: function(e, tag) {
     if (!this._flagIsActive(this.FLAG_CLEAN_CONDITIONALLY))
       return;
 
     var tagsList = e.getElementsByTagName(tag);
     var curTagsLength = tagsList.length;
+    var isList = tag === "ul" || tag === "ol";
 
     // Gather counts for other typical elements embedded within.
     // Traverse backwards so we can remove nodes at the same time
     // without effecting the traversal.
     //
     // TODO: Consider taking into account original contentScore here.
     for (var i = curTagsLength-1; i >= 0; i -= 1) {
       var weight = this._getClassWeight(tagsList[i]);
@@ -1627,23 +1644,23 @@ Readability.prototype = {
             embedCount += 1;
         }
 
         var linkDensity = this._getLinkDensity(tagsList[i]);
         var contentLength = this._getInnerText(tagsList[i]).length;
         var toRemove = false;
         if (img > p && !this._hasAncestorTag(tagsList[i], "figure")) {
           toRemove = true;
-        } else if (li > p && tag !== "ul" && tag !== "ol") {
+        } else if (!isList && li > p) {
           toRemove = true;
-        } else if ( input > Math.floor(p/3) ) {
+        } else if (input > Math.floor(p/3)) {
           toRemove = true;
-        } else if (contentLength < 25 && (img === 0 || img > 2) ) {
+        } else if (!isList && contentLength < 25 && (img === 0 || img > 2)) {
           toRemove = true;
-        } else if (weight < 25 && linkDensity > 0.2) {
+        } else if (!isList && weight < 25 && linkDensity > 0.2) {
           toRemove = true;
         } else if (weight >= 25 && linkDensity > 0.5) {
           toRemove = true;
         } else if ((embedCount === 1 && contentLength < 75) || embedCount > 1) {
           toRemove = true;
         }
 
         if (toRemove) {
@@ -1658,17 +1675,17 @@ Readability.prototype = {
    *
    * @param Element
    * @return void
   **/
   _cleanHeaders: function(e) {
     for (var headerIndex = 1; headerIndex < 3; headerIndex += 1) {
       var headers = e.getElementsByTagName('h' + headerIndex);
       for (var i = headers.length - 1; i >= 0; i -= 1) {
-        if (this._getClassWeight(headers[i]) < 0 || this._getLinkDensity(headers[i]) > 0.33)
+        if (this._getClassWeight(headers[i]) < 0)
           headers[i].parentNode.removeChild(headers[i]);
       }
     }
   },
 
   _flagIsActive: function(flag) {
     return (this._flags & flag) > 0;
   },
@@ -1681,42 +1698,52 @@ Readability.prototype = {
     this._flags = this._flags & ~flag;
   },
 
   /**
    * Decides whether or not the document is reader-able without parsing the whole thing.
    *
    * @return boolean Whether or not we suspect parse() will suceeed at returning an article object.
    */
-  isProbablyReaderable: function() {
-    var nodes = this._doc.getElementsByTagName("p");
-    if (nodes.length < 5) {
-      return false;
-    }
+  isProbablyReaderable: function(helperIsVisible) {
+    var nodes = this._getAllNodesWithTag(this._doc, ["p", "pre"]);
+
+    // FIXME we should have a fallback for helperIsVisible, but this is
+    // problematic because of jsdom's elem.style handling - see
+    // https://github.com/mozilla/readability/pull/186 for context.
 
-    var possibleParagraphs = 0;
-    for (var i = 0; i < nodes.length; i++) {
-      var node = nodes[i];
+    var score = 0;
+    // This is a little cheeky, we use the accumulator 'score' to decide what to return from
+    // this callback:
+    return this._someNode(nodes, function(node) {
+      if (helperIsVisible && !helperIsVisible(node))
+        return false;
       var matchString = node.className + " " + node.id;
 
       if (this.REGEXPS.unlikelyCandidates.test(matchString) &&
           !this.REGEXPS.okMaybeItsACandidate.test(matchString)) {
-        continue;
+        return false;
       }
 
-      if (node.textContent.trim().length < 100) {
-        continue;
+      if (node.matches && node.matches("li p")) {
+        return false;
       }
 
-      possibleParagraphs++;
-      if (possibleParagraphs >= 5) {
+      var textContentLength = node.textContent.trim().length;
+      if (textContentLength < 140) {
+        return false;
+      }
+
+      score += Math.sqrt(textContentLength - 140);
+
+      if (score > 20) {
         return true;
       }
-    }
-    return false;
+      return false;
+    });
   },
 
   /**
    * Runs readability.
    *
    * Workflow:
    *  1. Prep the document by removing script tags, css, etc.
    *  2. Build readability's DOM tree.