diff --git a/src/resources/markdown_template.js b/src/resources/markdown_template.js
index 1ac22293..bbc021ca 100644
--- a/src/resources/markdown_template.js
+++ b/src/resources/markdown_template.js
@@ -1546,6 +1546,10 @@ var htmlToText = function(identifier, id, timeStamp, html) {
     ts.addRule('mark', {
         filter: 'mark',
         replacement: function(content, node, options) {
+            if (!content) {
+                return '';
+            }
+
             return '<mark>' + content + '</mark>';
         }
     });
@@ -1576,6 +1580,44 @@ var htmlToText = function(identifier, id, timeStamp, html) {
         }
     });
 
+    ts.remove(['head', 'style']);
+
+    var subEnabled = false, supEnabled = false;
+    if (typeof VMarkdownitOption != "undefined") {
+        subEnabled = VMarkdownitOption.sub;
+        supEnabled = VMarkdownitOption.sup;
+    }
+
+    ts.addRule('sub_fix', {
+        filter: 'sub',
+        replacement: function (content, node, options) {
+            if (!content) {
+                return '';
+            }
+
+            if (subEnabled) {
+                return '~' + content + '~';
+            } else {
+                return '<sub>' + content + '</sub>';
+            }
+        }
+    });
+
+    ts.addRule('sup_fix', {
+        filter: 'sup',
+        replacement: function (content, node, options) {
+            if (!content) {
+                return '';
+            }
+
+            if (supEnabled) {
+                return '^' + content + '^';
+            } else {
+                return '<sup>' + content + '</sup>';
+            }
+        }
+    });
+
     var markdown = ts.turndown(html);
     content.htmlToTextCB(identifier, id, timeStamp, markdown);
 };
diff --git a/src/resources/mathjax_preview.js b/src/resources/mathjax_preview.js
index b00faa91..a765fbcb 100644
--- a/src/resources/mathjax_preview.js
+++ b/src/resources/mathjax_preview.js
@@ -72,7 +72,7 @@ var previewMathJax = function(identifier, id, timeStamp, text, isHtml) {
                            p,
                            [postProcessMathJax, identifier, id, timeStamp, p, isBlock]]);
     } catch (err) {
-        console.log("err: " + err);
+        content.setLog("err: " + err);
         content.mathjaxResultReady(identifier, id, timeStamp, 'png', '');
         contentDiv.removeChild(p);
         delete p;
@@ -94,7 +94,7 @@ var postProcessMathJax = function(identifier, id, timeStamp, container, isBlock)
         contentDiv.removeChild(container);
         delete container;
     }).catch(function (err) {
-        console.log("err: " + err);
+        content.setLog("err: " + err);
         content.mathjaxResultReady(identifier, id, timeStamp, 'png', '');
         contentDiv.removeChild(container);
         delete container;
@@ -132,7 +132,7 @@ var previewDiagram = function(identifier, id, timeStamp, lang, text) {
         try {
             var graph = flowchart.parse(text);
         } catch (err) {
-            console.log("err: " + err);
+            content.setLog("err: " + err);
             content.diagramResultReady(identifier, id, timeStamp, 'png', '');
             return;
         }
@@ -152,7 +152,7 @@ var previewDiagram = function(identifier, id, timeStamp, lang, text) {
         try {
             graph.drawSVG(div.id);
         } catch (err) {
-            console.log("err: " + err);
+            content.setLog("err: " + err);
             contentDiv.removeChild(div);
             delete div;
             content.diagramResultReady(identifier, id, timeStamp, 'png', '');
@@ -167,7 +167,7 @@ var previewDiagram = function(identifier, id, timeStamp, lang, text) {
                                           text,
                                           function(){});
         } catch (err) {
-            console.log("err: " + err);
+            content.setLog("err: " + err);
             content.diagramResultReady(identifier, id, timeStamp, 'png', '');
             return;
         }
@@ -197,7 +197,7 @@ var previewDiagram = function(identifier, id, timeStamp, lang, text) {
         contentDiv.removeChild(div);
         delete div;
     }).catch(function (err) {
-        console.log("err: " + err);
+        content.setLog("err: " + err);
         contentDiv.removeChild(div);
         content.diagramResultReady(identifier, id, timeStamp, 'png', '');
         delete div;