diff --git a/lib/ace/mode/markdown_highlight_rules.js b/lib/ace/mode/markdown_highlight_rules.js
index d3a784f4c62..d532455df26 100644
--- a/lib/ace/mode/markdown_highlight_rules.js
+++ b/lib/ace/mode/markdown_highlight_rules.js
@@ -35,6 +35,8 @@ var modes = require("../config").$modes;
 
 var oop = require("../lib/oop");
 var lang = require("../lib/lang");
+var useragent = require("../lib/useragent");
+    
 var TextHighlightRules = require("./text_highlight_rules").TextHighlightRules;
 var HtmlHighlightRules = require("./html_highlight_rules").HtmlHighlightRules;
 
@@ -121,7 +123,8 @@ var MarkdownHighlightRules = function() {
     }, {
         include : "basic"
     });
-
+    
+    
     this.addRules({
         "basic" : [{
             token : "constant.language.escape",
@@ -147,9 +150,9 @@ var MarkdownHighlightRules = function() {
             token : "string.strong",
             regex : "([*]{2}|[_]{2}(?=\\S))(.*?\\S[*_]*)(\\1)"
         }, { // emphasis * _
-            token : "string.emphasis",
-            regex : "([*]|[_](?=\\S))(.*?\\S[*_]*)(\\1)"
-        }, { //
+            token : "string.emphasis",            
+            regex : useragent.isIE ? "([*_])[^*_]*\\1(?=\\s|$)" : "(?<=\\s|^)([*_])[^*_]*\\1(?=\\s|$)"
+        }, { // highlight urls
             token : ["text", "url", "text"],
             regex : "(<)("+
                       "(?:https?|ftp|dict):[^'\">\\s]+"+