--- a/toolkit/locales/en-US/chrome/mozapps/downloads/unknownContentType.properties
+++ b/toolkit/locales/en-US/chrome/mozapps/downloads/unknownContentType.properties
@@ -17,16 +17,17 @@
 # The Initial Developer of the Original Code is
 # Doron Rosenberg.
 # Portions created by the Initial Developer are Copyright (C) 2001
 # the Initial Developer. All Rights Reserved.
 #
 # Contributor(s):
 #   Ben Goodger <ben@bengoodger.com>
 #   Rich Walsh <dragtext@e-vertise.com>
+#   Kailas Patil <patilkr24@gmail.com>
 #
 # Alternatively, the contents of this file may be used under the terms of
 # either the GNU General Public License Version 2 or later (the "GPL"), or
 # the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 # in which case the provisions of the GPL or the LGPL are applicable instead
 # of those above. If you wish to allow use of your version of this file only
 # under the terms of either the GPL or the LGPL, and not to allow others to
 # use your version of this file under the terms of the MPL, indicate your
@@ -44,16 +45,18 @@ chooseAppFilePickerTitle=Choose Helper A
 badApp=The application you chose ("%S") could not be found.  Check the file name or choose another application.
 badApp.title=Application not found
 badPermissions=The file could not be saved because you do not have the proper permissions.  Choose another save directory.
 badPermissions.title=Invalid Save Permissions
 selectDownloadDir=Select Download Folder
 unknownAccept.label=Save File
 unknownCancel.label=Cancel
 fileType=%S file
+# LOCALIZATION NOTE (fileSizeWithType): first %S is type, second %S is size, and third %S is unit  
+fileSizeWithType=%1S (%2S %3S)
 
 # LOCALIZATION NOTE (wpsDefaultOS2): OS/2 only, WPS refers to the Workplace Shell and should probably not be translated
 wpsDefaultOS2=WPS Default
 # LOCALIZATION NOTE (classViewerOS2): OS/2 only
 classViewerOS2=Viewer for Class %S
 # LOCALIZATION NOTE (mmImageViewerOS2): OS/2 only, default operation of image files with OS/2 multimedia support installed
 mmImageViewerOS2=Image Viewer
 # LOCALIZATION NOTE (mmAudioPlayerOS2): OS/2 only, default operation of audio files with OS/2 multimedia support installed

--- a/toolkit/mozapps/downloads/nsHelperAppDlg.js
+++ b/toolkit/mozapps/downloads/nsHelperAppDlg.js
@@ -24,16 +24,17 @@
 # Contributor(s):
 #   Bill Law <law@netscape.com>
 #   Scott MacGregor <mscott@netscape.com>
 #   Ben Goodger <ben@bengoodger.com> (2.0)
 #   Fredrik Holmqvist <thesuckiestemail@yahoo.se>
 #   Dan Mosedale <dmose@mozilla.org>
 #   Jim Mathies <jmathies@mozilla.com>
 #   Ehsan Akhgari <ehsan.akhgari@gmail.com>
+#   Kailas Patil <patilkr24@gmail.com>
 #
 # Alternatively, the contents of this file may be used under the terms of
 # either the GNU General Public License Version 2 or later (the "GPL"), or
 # the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 # in which case the provisions of the GPL or the LGPL are applicable instead
 # of those above. If you wish to allow use of your version of this file only
 # under the terms of either the GPL or the LGPL, and not to allow others to
 # use your version of this file under the terms of the MPL, indicate your
@@ -134,16 +135,17 @@ nsUnkownContentTypeDialogProgressListene
  */
 
 const PREF_BD_USEDOWNLOADDIR = "browser.download.useDownloadDir";
 const nsITimer = Components.interfaces.nsITimer;
 
 Components.utils.import("resource://gre/modules/XPCOMUtils.jsm");
 Components.utils.import("resource://gre/modules/DownloadLastDir.jsm");
 Components.utils.import("resource://gre/modules/DownloadPaths.jsm");
+Components.utils.import("resource://gre/modules/DownloadUtils.jsm");
 
 /* ctor
  */
 function nsUnknownContentTypeDialog() {
   // Initialize data properties.
   this.mLauncher = null;
   this.mContext  = null;
   this.mSourcePath = null;
@@ -604,18 +606,26 @@ nsUnknownContentTypeDialog.prototype = {
       catch (ex) {
       }
       if (primaryExtension != "")
         typeString = this.dialogElement("strings").getFormattedString("fileType", [primaryExtension.toUpperCase()]);
       // 3. If we can't even do that, just give up and show the MIME type.
       else
         typeString = mimeInfo.MIMEType;
     }
-
-    type.value = typeString;
+    if (this.mLauncher.contentLength) {
+      let [size, unit] = DownloadUtils.
+                         convertByteUnits(this.mLauncher.contentLength);
+      type.value = this.dialogElement("strings")
+                       .getFormattedString("fileSizeWithType", 
+                                           [typeString, size, unit]);
+    }
+    else {
+      type.value = typeString;
+    }
   },
 
   _blurred: false,
   _delayExpired: false,
   onBlur: function(aEvent) {
     this._blurred = true;
     this.mDialog.document.documentElement.getButton("accept").disabled = true;
   },