diff --git a/public/js/extra.js b/public/js/extra.js
index a2ae83f6..28a91fbc 100644
--- a/public/js/extra.js
+++ b/public/js/extra.js
@@ -338,13 +338,6 @@ function finishView(view) {
 //only static transform should be here
 function postProcess(code) {
     var result = $('<div>' + code + '</div>');
-    //prevent XSS
-    result.find("script").replaceWith(function () {
-        return "<noscript>" + $(this).html() + "</noscript>"
-    });
-    result.find("iframe").replaceWith(function () {
-        return "<noiframe>" + $(this).html() + "</noiframe>"
-    });
     //link should open in new window or tab
     result.find('a:not([href^="#"]):not([target])').attr('target', '_blank');
 	//update continue line numbers
@@ -576,11 +569,11 @@ function autoLinkify(view) {
 }
 
 function deduplicatedHeaderId(view) {
-    var headers = view.find(':header').toArray();
+    var headers = view.find(':header.raw').removeClass('raw').toArray();
     for (var i = 0; i < headers.length; i++) {
         var id = $(headers[i]).attr('id');
         if (!id) continue;
-        var duplicatedHeaders = view.find(':header[id=' + id + ']').toArray();
+        var duplicatedHeaders = view.find(':header[id="' + id + '"]').toArray();
         for (var j = 0; j < duplicatedHeaders.length; j++) {
             if (duplicatedHeaders[j] != headers[i]) {
                 var newId = id + j;
@@ -685,6 +678,9 @@ md.renderer.rules.list_item_open = function ( /* tokens, idx, options, env */ )
 md.renderer.rules.blockquote_open = function (tokens, idx /*, options, env */ ) {
     return '<blockquote class="raw">\n';
 };
+md.renderer.rules.heading_open = function (tokens, idx) {
+    return '<h' + tokens[idx].hLevel + ' class="raw">';
+};
 md.renderer.rules.fence = function (tokens, idx, options, env, self) {
     var token = tokens[idx];
     var langClass = '';
diff --git a/public/js/index.js b/public/js/index.js
index 2e797ac3..3507e016 100644
--- a/public/js/index.js
+++ b/public/js/index.js
@@ -2132,10 +2132,15 @@ var lastResult = null;
 function updateViewInner() {
     if (currentMode == modeType.edit || !isDirty) return;
     var value = editor.getValue();
+    var lastMeta = md.meta;
     md.meta = {};
-    md.render(value); //only for get meta
-    parseMeta(md, ui.area.markdown, $('#toc'), $('#toc-affix'));
     var rendered = md.render(value);
+    // only render again when meta changed
+    if (JSON.stringify(md.meta) != JSON.stringify(lastMeta)) {
+        parseMeta(md, ui.area.markdown, $('#toc'), $('#toc-affix'));
+        rendered = md.render(value);
+    }
+    // prevent XSS
     rendered = preventXSS(rendered);
     var result = postProcess(rendered).children().toArray();
     partialUpdate(result, lastResult, ui.area.markdown.children().toArray());
diff --git a/public/js/pretty.js b/public/js/pretty.js
index a38dc244..40d90cf7 100644
--- a/public/js/pretty.js
+++ b/public/js/pretty.js
@@ -1,9 +1,14 @@
 var markdown = $(".markdown-body");
 var text = $('<textarea/>').html(markdown.html()).text();
+var lastMeta = md.meta;
 md.meta = {};
-md.render(text); //only for get meta
-parseMeta(md, markdown, $('#toc'), $('#toc-affix'));
 var rendered = md.render(text);
+// only render again when meta changed
+if (JSON.stringify(md.meta) != JSON.stringify(lastMeta)) {
+    parseMeta(md, markdown, $('#toc'), $('#toc-affix'));
+    rendered = md.render(text);
+}
+// prevent XSS
 rendered = preventXSS(rendered);
 var result = postProcess(rendered);
 markdown.html(result.html());
diff --git a/public/js/syncscroll.js b/public/js/syncscroll.js
index c3793a88..abc9a274 100644
--- a/public/js/syncscroll.js
+++ b/public/js/syncscroll.js
@@ -73,9 +73,9 @@ md.renderer.rules.heading_open = function (tokens, idx) {
     if (tokens[idx].lines && tokens[idx].level === 0) {
         var startline = tokens[idx].lines[0] + 1;
         var endline = tokens[idx].lines[1];
-        return '<h' + tokens[idx].hLevel + ' class="part" data-startline="' + startline + '" data-endline="' + endline + '">';
+        return '<h' + tokens[idx].hLevel + ' class="part raw" data-startline="' + startline + '" data-endline="' + endline + '">';
     }
-    return '<h' + tokens[idx].hLevel + '>';
+    return '<h' + tokens[idx].hLevel + ' class="raw">';
 };
 
 md.renderer.rules.fence = function (tokens, idx, options, env, self) {