diff --git a/mozilla/content/html/document/src/nsHTMLDocument.cpp b/mozilla/content/html/document/src/nsHTMLDocument.cpp
index 9d81d8e45c5..b358ffd2440 100644
--- a/mozilla/content/html/document/src/nsHTMLDocument.cpp
+++ b/mozilla/content/html/document/src/nsHTMLDocument.cpp
@@ -1957,7 +1957,8 @@ nsHTMLDocument::GetSourceDocumentURI(nsIURI** sourceURI)
 
 // XXX TBI: accepting arguments to the open method.
 nsresult
-nsHTMLDocument::OpenCommon(nsIURI* aSourceURI, PRBool aReplace)
+nsHTMLDocument::OpenCommon(nsIURI* aSourceURI, const nsACString& aContentType,
+                           PRBool aReplace)
 {
   // If we already have a parser we ignore the document.open call.
   if (mParser) {
@@ -2077,6 +2078,9 @@ nsHTMLDocument::OpenCommon(nsIURI* aSourceURI, PRBool aReplace)
 
   mParser = do_CreateInstance(kCParserCID, &rv);
 
+  // This will be propagated to the parser when someone actually calls write()
+  mContentType = aContentType;
+
   mIsWriting = 1;
 
   if (NS_SUCCEEDED(rv)) {
@@ -2137,11 +2141,12 @@ NS_IMETHODIMP
 nsHTMLDocument::Open()
 {
   nsCOMPtr<nsIDOMDocument> doc;
-  return Open(PR_FALSE, getter_AddRefs(doc));
+  return Open(NS_LITERAL_CSTRING("text/html"), PR_FALSE, getter_AddRefs(doc));
 }
 
 NS_IMETHODIMP
-nsHTMLDocument::Open(PRBool aReplace, nsIDOMDocument** aReturn)
+nsHTMLDocument::Open(const nsACString& aContentType, PRBool aReplace,
+                     nsIDOMDocument** aReturn)
 {
   // XXX The URI of the newly created document will match
   // that of the source document. Is this right?
@@ -2157,7 +2162,7 @@ nsHTMLDocument::Open(PRBool aReplace, nsIDOMDocument** aReturn)
   }
   NS_ENSURE_SUCCESS(rv, rv);
 
-  rv = OpenCommon(sourceURI, aReplace);
+  rv = OpenCommon(sourceURI, aContentType, aReplace);
   NS_ENSURE_SUCCESS(rv, rv);
 
   return CallQueryInterface(this, aReturn);
@@ -2179,10 +2184,12 @@ nsHTMLDocument::Close()
 
   if (mParser && mIsWriting) {
     ++mWriteLevel;
-    rv = mParser->Parse(NS_LITERAL_STRING("</HTML>"),
-                        NS_GENERATE_PARSER_KEY(),
-                        NS_LITERAL_CSTRING("text/html"), PR_FALSE,
-                        PR_TRUE);
+    if (mContentType.EqualsLiteral("text/html")) {
+      rv = mParser->Parse(NS_LITERAL_STRING("</HTML>"),
+                          NS_GENERATE_PARSER_KEY(),
+                          mContentType, PR_FALSE,
+                          PR_TRUE);
+    }
     --mWriteLevel;
     mIsWriting = 0;
     mParser = nsnull;
@@ -2260,12 +2267,12 @@ nsHTMLDocument::WriteCommon(const nsAString& aText,
   if (aNewlineTerminate) {
     rv = mParser->Parse(aText + new_line,
                         NS_GENERATE_PARSER_KEY(),
-                        NS_LITERAL_CSTRING("text/html"), PR_FALSE,
+                        mContentType, PR_FALSE,
                         (!mIsWriting || (mWriteLevel > 1)));
   } else {
     rv = mParser->Parse(aText,
                         NS_GENERATE_PARSER_KEY(),
-                        NS_LITERAL_CSTRING("text/html"), PR_FALSE,
+                        mContentType, PR_FALSE,
                         (!mIsWriting || (mWriteLevel > 1)));
   }
 
diff --git a/mozilla/content/html/document/src/nsHTMLDocument.h b/mozilla/content/html/document/src/nsHTMLDocument.h
index 7afc447573e..7246b828078 100644
--- a/mozilla/content/html/document/src/nsHTMLDocument.h
+++ b/mozilla/content/html/document/src/nsHTMLDocument.h
@@ -247,7 +247,8 @@ protected:
   nsresult WriteCommon(const nsAString& aText,
                        PRBool aNewlineTerminate);
   nsresult ScriptWriteCommon(PRBool aNewlineTerminate);
-  nsresult OpenCommon(nsIURI* aUrl, PRBool aReplace);
+  nsresult OpenCommon(nsIURI* aUrl, const nsACString& aContentType,
+                      PRBool aReplace);
 
   nsresult CreateAndAddWyciwygChannel(void);
   nsresult RemoveWyciwygChannel(void);
diff --git a/mozilla/dom/public/idl/html/nsIDOMNSHTMLDocument.idl b/mozilla/dom/public/idl/html/nsIDOMNSHTMLDocument.idl
index f39a7470684..4f8fb5b9004 100644
--- a/mozilla/dom/public/idl/html/nsIDOMNSHTMLDocument.idl
+++ b/mozilla/dom/public/idl/html/nsIDOMNSHTMLDocument.idl
@@ -57,9 +57,13 @@ interface nsIDOMNSHTMLDocument : nsISupports
 
   // This is the internal version of open(); note that the version
   // scriptable with JS is defined entirely in classinfo.
+  // If aContentType is not something supported by nsHTMLDocument and
+  // the HTML content sink, trying to write to the document will
+  // probably throw.
   // Pass aReplace = true to trigger a replacement of the previous
   // document in session history; pass false for normal history handling.
-  nsIDOMDocument            open(in boolean aReplace);
+  nsIDOMDocument            open(in ACString aContentType,
+                                 in boolean aReplace);
 
   // Scriptable versions of write(), writeln(), clear().
   void                      write();
diff --git a/mozilla/dom/src/base/nsDOMClassInfo.cpp b/mozilla/dom/src/base/nsDOMClassInfo.cpp
index 7bf6043ab4d..e4f63c1ef97 100644
--- a/mozilla/dom/src/base/nsDOMClassInfo.cpp
+++ b/mozilla/dom/src/base/nsDOMClassInfo.cpp
@@ -5396,6 +5396,22 @@ nsHTMLDocumentSH::DocumentOpen(JSContext *cx, JSObject *obj, uintN argc,
   nsCOMPtr<nsIDOMNSHTMLDocument> doc(do_QueryInterface(native));
   NS_ENSURE_TRUE(doc, JS_FALSE);
 
+  nsCAutoString contentType;
+  if (argc > 0) {
+    JSString* jsstr = JS_ValueToString(cx, argv[0]);
+    if (!jsstr) {
+      nsDOMClassInfo::ThrowJSException(cx, NS_ERROR_OUT_OF_MEMORY);
+      return JS_FALSE;
+    }
+    CopyUTF16toUTF8(NS_REINTERPRET_CAST(const PRUnichar*,
+                                        ::JS_GetStringChars(jsstr)),
+                    contentType);
+    ToLowerCase(contentType);
+  }
+  if (!contentType.EqualsLiteral("text/plain")){
+    contentType = "text/html";
+  }
+  
   PRBool replace = PR_FALSE;
   if (argc > 1) {
     JSString* jsstr = JS_ValueToString(cx, argv[1]);
@@ -5410,7 +5426,7 @@ nsHTMLDocumentSH::DocumentOpen(JSContext *cx, JSObject *obj, uintN argc,
   }
 
   nsCOMPtr<nsIDOMDocument> retval;
-  rv = doc->Open(replace, getter_AddRefs(retval));
+  rv = doc->Open(contentType, replace, getter_AddRefs(retval));
   if (NS_FAILED(rv)) {
     nsDOMClassInfo::ThrowJSException(cx, rv);
 
diff --git a/mozilla/parser/htmlparser/src/nsExpatDriver.cpp b/mozilla/parser/htmlparser/src/nsExpatDriver.cpp
index c85afe08cc6..a559dca2de6 100644
--- a/mozilla/parser/htmlparser/src/nsExpatDriver.cpp
+++ b/mozilla/parser/htmlparser/src/nsExpatDriver.cpp
@@ -1099,8 +1099,9 @@ nsExpatDriver::GetMostDerivedIID(void) const
 NS_IMETHODIMP_(void)
 nsExpatDriver::Terminate()
 {
-  // XXX - not sure what happens to the unparsed data.
-  XML_BlockParser(mExpatParser);
+  if (mExpatParser) {
+    XML_BlockParser(mExpatParser); // XXX - not sure what happens to the unparsed data.
+  }
   mInternalState = NS_ERROR_HTMLPARSER_STOPPARSING;
 }