diff --git a/toolkit/components/viewsource/content/viewPartialSource.js b/toolkit/components/viewsource/content/viewPartialSource.js
index 8cb761cd60ad..feda67de9186 100644
--- a/toolkit/components/viewsource/content/viewPartialSource.js
+++ b/toolkit/components/viewsource/content/viewPartialSource.js
@@ -123,71 +123,78 @@ function viewPartialSourceForSelection(selection)
   var endPath = getPath(ancestorContainer, endContainer);
 
   // clone the fragment of interest and reset everything to be relative to it
-  // note: it is with the clone that we operate from now on
+  // note: it is with the clone that we operate/munge from now on
   ancestorContainer = ancestorContainer.cloneNode(true);
   startContainer = ancestorContainer;
   endContainer = ancestorContainer;
-  var i;
-  for (i = startPath ? startPath.length-1 : -1; i >= 0; i--) {
-    startContainer = startContainer.childNodes.item(startPath[i]);
-  }
-  for (i = endPath ? endPath.length-1 : -1; i >= 0; i--) {
-    endContainer = endContainer.childNodes.item(endPath[i]);
-  }
 
-  // add special markers to record the extent of the selection
-  // note: |startOffset| and |endOffset| are interpreted either as
-  // offsets in the text data or as child indices (see the Range spec)
-  // (here, munging the end point first to keep the start point safe...)
-  var tmpNode;
-  if (endContainer.nodeType == Node.TEXT_NODE ||
-      endContainer.nodeType == Node.CDATA_SECTION_NODE) {
-    // do some extra tweaks to try to avoid the view-source output to look like
-    // ...<tag>]... or ...]</tag>... (where ']' marks the end of the selection).
-    // To get a neat output, the idea here is to remap the end point from:
-    // 1. ...<tag>]...   to   ...]<tag>...
-    // 2. ...]</tag>...  to   ...</tag>]...
-    if ((endOffset > 0 && endOffset < endContainer.data.length) ||
-        !endContainer.parentNode || !endContainer.parentNode.parentNode)
-      endContainer.insertData(endOffset, MARK_SELECTION_END);
+  // Only bother with the selection if it can be remapped. Don't mess with
+  // leaf elements (such as <isindex>) that secretly use anynomous content
+  // for their display appearance.
+  var canDrawSelection = ancestorContainer.hasChildNodes();
+  if (canDrawSelection) {
+    var i;
+    for (i = startPath ? startPath.length-1 : -1; i >= 0; i--) {
+      startContainer = startContainer.childNodes.item(startPath[i]);
+    }
+    for (i = endPath ? endPath.length-1 : -1; i >= 0; i--) {
+      endContainer = endContainer.childNodes.item(endPath[i]);
+    }
+
+    // add special markers to record the extent of the selection
+    // note: |startOffset| and |endOffset| are interpreted either as
+    // offsets in the text data or as child indices (see the Range spec)
+    // (here, munging the end point first to keep the start point safe...)
+    var tmpNode;
+    if (endContainer.nodeType == Node.TEXT_NODE ||
+        endContainer.nodeType == Node.CDATA_SECTION_NODE) {
+      // do some extra tweaks to try to avoid the view-source output to look like
+      // ...<tag>]... or ...]</tag>... (where ']' marks the end of the selection).
+      // To get a neat output, the idea here is to remap the end point from:
+      // 1. ...<tag>]...   to   ...]<tag>...
+      // 2. ...]</tag>...  to   ...</tag>]...
+      if ((endOffset > 0 && endOffset < endContainer.data.length) ||
+          !endContainer.parentNode || !endContainer.parentNode.parentNode)
+        endContainer.insertData(endOffset, MARK_SELECTION_END);
+      else {
+        tmpNode = doc.createTextNode(MARK_SELECTION_END);
+        endContainer = endContainer.parentNode;
+        if (endOffset == 0)
+          endContainer.parentNode.insertBefore(tmpNode, endContainer);
+        else
+          endContainer.parentNode.insertBefore(tmpNode, endContainer.nextSibling);
+      }
+    }
     else {
       tmpNode = doc.createTextNode(MARK_SELECTION_END);
-      endContainer = endContainer.parentNode;
-      if (endOffset == 0)
-        endContainer.parentNode.insertBefore(tmpNode, endContainer);
-      else
-        endContainer.parentNode.insertBefore(tmpNode, endContainer.nextSibling);
+      endContainer.insertBefore(tmpNode, endContainer.childNodes.item(endOffset));
     }
-  }
-  else {
-    tmpNode = doc.createTextNode(MARK_SELECTION_END);
-    endContainer.insertBefore(tmpNode, endContainer.childNodes.item(endOffset));
-  }
 
-  if (startContainer.nodeType == Node.TEXT_NODE ||
-      startContainer.nodeType == Node.CDATA_SECTION_NODE) {
-    // do some extra tweaks to try to avoid the view-source output to look like
-    // ...<tag>[... or ...[</tag>... (where '[' marks the start of the selection).
-    // To get a neat output, the idea here is to remap the start point from:
-    // 1. ...<tag>[...   to   ...[<tag>...
-    // 2. ...[</tag>...  to   ...</tag>[...
-    if ((startOffset > 0 && startOffset < startContainer.data.length) ||
-        !startContainer.parentNode || !startContainer.parentNode.parentNode ||
-        startContainer != startContainer.parentNode.lastChild)
-      startContainer.insertData(startOffset, MARK_SELECTION_START);
+    if (startContainer.nodeType == Node.TEXT_NODE ||
+        startContainer.nodeType == Node.CDATA_SECTION_NODE) {
+      // do some extra tweaks to try to avoid the view-source output to look like
+      // ...<tag>[... or ...[</tag>... (where '[' marks the start of the selection).
+      // To get a neat output, the idea here is to remap the start point from:
+      // 1. ...<tag>[...   to   ...[<tag>...
+      // 2. ...[</tag>...  to   ...</tag>[...
+      if ((startOffset > 0 && startOffset < startContainer.data.length) ||
+          !startContainer.parentNode || !startContainer.parentNode.parentNode ||
+          startContainer != startContainer.parentNode.lastChild)
+        startContainer.insertData(startOffset, MARK_SELECTION_START);
+      else {
+        tmpNode = doc.createTextNode(MARK_SELECTION_START);
+        startContainer = startContainer.parentNode;
+        if (startOffset == 0)
+          startContainer.parentNode.insertBefore(tmpNode, startContainer);
+        else
+          startContainer.parentNode.insertBefore(tmpNode, startContainer.nextSibling);
+      }
+    }
     else {
       tmpNode = doc.createTextNode(MARK_SELECTION_START);
-      startContainer = startContainer.parentNode;
-      if (startOffset == 0)
-        startContainer.parentNode.insertBefore(tmpNode, startContainer);
-      else
-        startContainer.parentNode.insertBefore(tmpNode, startContainer.nextSibling);
+      startContainer.insertBefore(tmpNode, startContainer.childNodes.item(startOffset));
     }
   }
-  else {
-    tmpNode = doc.createTextNode(MARK_SELECTION_START);
-    startContainer.insertBefore(tmpNode, startContainer.childNodes.item(startOffset));
-  }
 
   // now extract and display the syntax highlighted source
   tmpNode = doc.createElementNS(NS_XHTML, 'div');
@@ -195,7 +202,9 @@ function viewPartialSourceForSelection(selection)
 
   // the load is aynchronous and so we will wait until the view-source DOM is done
   // before drawing the selection.
-  window.document.getElementById("appcontent").addEventListener("load", drawSelection, true);
+  if (canDrawSelection) {
+    window.document.getElementById("appcontent").addEventListener("load", drawSelection, true);
+  }
 
   // all our content is held by the data:URI and URIs are internally stored as utf-8 (see nsIURI.idl)
   var loadFlags = Components.interfaces.nsIWebNavigation.LOAD_FLAGS_BYPASS_CACHE;
diff --git a/xpfe/browser/resources/content/viewPartialSource.js b/xpfe/browser/resources/content/viewPartialSource.js
index 67ecd3f93253..190f7eec39cc 100644
--- a/xpfe/browser/resources/content/viewPartialSource.js
+++ b/xpfe/browser/resources/content/viewPartialSource.js
@@ -119,71 +119,78 @@ function viewPartialSourceForSelection(selection)
   var endPath = getPath(ancestorContainer, endContainer);
 
   // clone the fragment of interest and reset everything to be relative to it
-  // note: it is with the clone that we operate from now on
+  // note: it is with the clone that we operate/munge from now on
   ancestorContainer = ancestorContainer.cloneNode(true);
   startContainer = ancestorContainer;
   endContainer = ancestorContainer;
-  var i;
-  for (i = startPath ? startPath.length-1 : -1; i >= 0; i--) {
-    startContainer = startContainer.childNodes.item(startPath[i]);
-  }
-  for (i = endPath ? endPath.length-1 : -1; i >= 0; i--) {
-    endContainer = endContainer.childNodes.item(endPath[i]);
-  }
 
-  // add special markers to record the extent of the selection
-  // note: |startOffset| and |endOffset| are interpreted either as
-  // offsets in the text data or as child indices (see the Range spec)
-  // (here, munging the end point first to keep the start point safe...)
-  var tmpNode;
-  if (endContainer.nodeType == Node.TEXT_NODE ||
-      endContainer.nodeType == Node.CDATA_SECTION_NODE) {
-    // do some extra tweaks to try to avoid the view-source output to look like
-    // ...<tag>]... or ...]</tag>... (where ']' marks the end of the selection).
-    // To get a neat output, the idea here is to remap the end point from:
-    // 1. ...<tag>]...   to   ...]<tag>...
-    // 2. ...]</tag>...  to   ...</tag>]...
-    if ((endOffset > 0 && endOffset < endContainer.data.length) ||
-        !endContainer.parentNode || !endContainer.parentNode.parentNode)
-      endContainer.insertData(endOffset, MARK_SELECTION_END);
+  // Only bother with the selection if it can be remapped. Don't mess with
+  // leaf elements (such as <isindex>) that secretly use anynomous content
+  // for their display appearance.
+  var canDrawSelection = ancestorContainer.hasChildNodes();
+  if (canDrawSelection) {
+    var i;
+    for (i = startPath ? startPath.length-1 : -1; i >= 0; i--) {
+      startContainer = startContainer.childNodes.item(startPath[i]);
+    }
+    for (i = endPath ? endPath.length-1 : -1; i >= 0; i--) {
+      endContainer = endContainer.childNodes.item(endPath[i]);
+    }
+
+    // add special markers to record the extent of the selection
+    // note: |startOffset| and |endOffset| are interpreted either as
+    // offsets in the text data or as child indices (see the Range spec)
+    // (here, munging the end point first to keep the start point safe...)
+    var tmpNode;
+    if (endContainer.nodeType == Node.TEXT_NODE ||
+        endContainer.nodeType == Node.CDATA_SECTION_NODE) {
+      // do some extra tweaks to try to avoid the view-source output to look like
+      // ...<tag>]... or ...]</tag>... (where ']' marks the end of the selection).
+      // To get a neat output, the idea here is to remap the end point from:
+      // 1. ...<tag>]...   to   ...]<tag>...
+      // 2. ...]</tag>...  to   ...</tag>]...
+      if ((endOffset > 0 && endOffset < endContainer.data.length) ||
+          !endContainer.parentNode || !endContainer.parentNode.parentNode)
+        endContainer.insertData(endOffset, MARK_SELECTION_END);
+      else {
+        tmpNode = doc.createTextNode(MARK_SELECTION_END);
+        endContainer = endContainer.parentNode;
+        if (endOffset == 0)
+          endContainer.parentNode.insertBefore(tmpNode, endContainer);
+        else
+          endContainer.parentNode.insertBefore(tmpNode, endContainer.nextSibling);
+      }
+    }
     else {
       tmpNode = doc.createTextNode(MARK_SELECTION_END);
-      endContainer = endContainer.parentNode;
-      if (endOffset == 0)
-        endContainer.parentNode.insertBefore(tmpNode, endContainer);
-      else
-        endContainer.parentNode.insertBefore(tmpNode, endContainer.nextSibling);
+      endContainer.insertBefore(tmpNode, endContainer.childNodes.item(endOffset));
     }
-  }
-  else {
-    tmpNode = doc.createTextNode(MARK_SELECTION_END);
-    endContainer.insertBefore(tmpNode, endContainer.childNodes.item(endOffset));
-  }
 
-  if (startContainer.nodeType == Node.TEXT_NODE ||
-      startContainer.nodeType == Node.CDATA_SECTION_NODE) {
-    // do some extra tweaks to try to avoid the view-source output to look like
-    // ...<tag>[... or ...[</tag>... (where '[' marks the start of the selection).
-    // To get a neat output, the idea here is to remap the start point from:
-    // 1. ...<tag>[...   to   ...[<tag>...
-    // 2. ...[</tag>...  to   ...</tag>[...
-    if ((startOffset > 0 && startOffset < startContainer.data.length) ||
-        !startContainer.parentNode || !startContainer.parentNode.parentNode ||
-        startContainer != startContainer.parentNode.lastChild)
-      startContainer.insertData(startOffset, MARK_SELECTION_START);
+    if (startContainer.nodeType == Node.TEXT_NODE ||
+        startContainer.nodeType == Node.CDATA_SECTION_NODE) {
+      // do some extra tweaks to try to avoid the view-source output to look like
+      // ...<tag>[... or ...[</tag>... (where '[' marks the start of the selection).
+      // To get a neat output, the idea here is to remap the start point from:
+      // 1. ...<tag>[...   to   ...[<tag>...
+      // 2. ...[</tag>...  to   ...</tag>[...
+      if ((startOffset > 0 && startOffset < startContainer.data.length) ||
+          !startContainer.parentNode || !startContainer.parentNode.parentNode ||
+          startContainer != startContainer.parentNode.lastChild)
+        startContainer.insertData(startOffset, MARK_SELECTION_START);
+      else {
+        tmpNode = doc.createTextNode(MARK_SELECTION_START);
+        startContainer = startContainer.parentNode;
+        if (startOffset == 0)
+          startContainer.parentNode.insertBefore(tmpNode, startContainer);
+        else
+          startContainer.parentNode.insertBefore(tmpNode, startContainer.nextSibling);
+      }
+    }
     else {
       tmpNode = doc.createTextNode(MARK_SELECTION_START);
-      startContainer = startContainer.parentNode;
-      if (startOffset == 0)
-        startContainer.parentNode.insertBefore(tmpNode, startContainer);
-      else
-        startContainer.parentNode.insertBefore(tmpNode, startContainer.nextSibling);
+      startContainer.insertBefore(tmpNode, startContainer.childNodes.item(startOffset));
     }
   }
-  else {
-    tmpNode = doc.createTextNode(MARK_SELECTION_START);
-    startContainer.insertBefore(tmpNode, startContainer.childNodes.item(startOffset));
-  }
 
   // now extract and display the syntax highlighted source
   tmpNode = doc.createElementNS(NS_XHTML, 'div');
@@ -191,7 +198,9 @@ function viewPartialSourceForSelection(selection)
 
   // the load is aynchronous and so we will wait until the view-source DOM is done
   // before drawing the selection.
-  window.document.getElementById("appcontent").addEventListener("load", drawSelection, true);
+  if (canDrawSelection) {
+    window.document.getElementById("appcontent").addEventListener("load", drawSelection, true);
+  }
 
   // all our content is held by the data:URI and URIs are internally stored as utf-8 (see nsIURI.idl)
   var loadFlags = Components.interfaces.nsIWebNavigation.LOAD_FLAGS_BYPASS_CACHE;