diff --git a/layout/tools/reftest/README.txt b/layout/tools/reftest/README.txt
index ee1880bf79c..d688fdd04a5 100644
--- a/layout/tools/reftest/README.txt
+++ b/layout/tools/reftest/README.txt
@@ -33,9 +33,10 @@ running tests at any time to see whether they still pass.
 Manifest Format
 ===============
 
-The test manifest format is a plain text file.  The "#" makes the
-remainder of a line a comment.  Each non-blank line (after removal of
-comments) must be one of the following:
+The test manifest format is a plain text file.  A line starting with a
+"#" is a comment.  Lines may be commented using whitespace followed by
+a "#" and the comment.  Each non-blank line (after removal of comments)
+must be one of the following:
 
 1. Inclusion of another manifest
 
diff --git a/layout/tools/reftest/reftest.js b/layout/tools/reftest/reftest.js
index aa935834fee..aadb2d4d82a 100644
--- a/layout/tools/reftest/reftest.js
+++ b/layout/tools/reftest/reftest.js
@@ -145,9 +145,11 @@ function ReadManifest(aURL)
         var more = lis.readLine(line);
         ++lineNo;
         var str = line.value;
-        str = /^[^#]*/.exec(str)[0]; // strip everything after "#"
-        if (!str)
+        if (str.charAt(0) == "#")
             continue; // entire line was a comment
+        var i = str.search(/\s+#/);
+        if (i >= 0)
+            str = str.substring(0, i);
         // strip leading and trailing whitespace
         str = str.replace(/^\s*/, '').replace(/\s*$/, '');
         if (!str || str == "")
@@ -386,7 +388,8 @@ function DocumentLoaded()
     /* XXX This needs to be rgb(255,255,255) because otherwise we get
      * black bars at the bottom of every test that are different size
      * for the first test and the rest (scrollbar-related??) */
-    canvas.getContext("2d").drawWindow(gBrowser.contentWindow, 0, 0,
+    var win = gBrowser.contentWindow;
+    canvas.getContext("2d").drawWindow(win, win.scrollX, win.scrollY,
                                        canvas.width, canvas.height, "rgb(255,255,255)");
 
     switch (gState) {