diff --git a/mozilla/htmlparser/src/CNavDTD.cpp b/mozilla/htmlparser/src/CNavDTD.cpp
index e0750f9a8b6..e43eaaeadfc 100644
--- a/mozilla/htmlparser/src/CNavDTD.cpp
+++ b/mozilla/htmlparser/src/CNavDTD.cpp
@@ -9,7 +9,7 @@
  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the NPL
  * for the specific language governing rights and limitations under the
  * NPL.
- *
+ * 
  * The Initial Developer of this code under the NPL is Netscape
  * Communications Corporation.  Portions created by Netscape are
  * Copyright (C) 1998 Netscape Communications Corporation.  All Rights
@@ -361,7 +361,7 @@ CNavDTD::CNavDTD() : nsIDTD(), mTokenDeque(gTokenKiller)  {
   nsCRT::zero(mTokenHandlers,sizeof(mTokenHandlers));
   mHasOpenForm=PR_FALSE;
   mHasOpenMap=PR_FALSE;
-  InitializeDefaultTokenHandlers();
+  InitializeDefaultTokenHandlers(); 
   mHeadContext=new nsDTDContext();
   mBodyContext=new nsDTDContext();
   mFormContext=0;
@@ -1905,7 +1905,13 @@ PRBool CNavDTD::CanOmit(eHTMLTags aParent,eHTMLTags aChild) const {
           result=HasOpenContainer(aChild); //don't bother if they're already open...
           break;
 
-        case eHTMLTag_button:       case eHTMLTag_fieldset:
+          //The following line was commented out to fix bug 1166. 
+          //Effectively, this allows a button to exist anywhere in the document,
+          //and not just inside a form.
+
+        //case eHTMLTag_button:       
+
+        case eHTMLTag_fieldset:
         case eHTMLTag_input:        case eHTMLTag_isindex:
         case eHTMLTag_label:        case eHTMLTag_legend:
         case eHTMLTag_select:       case eHTMLTag_textarea:
diff --git a/mozilla/htmlparser/src/nsDTDUtils.cpp b/mozilla/htmlparser/src/nsDTDUtils.cpp
index a3a9df7fb8e..86ac19275a3 100644
--- a/mozilla/htmlparser/src/nsDTDUtils.cpp
+++ b/mozilla/htmlparser/src/nsDTDUtils.cpp
@@ -19,7 +19,7 @@
 
 #include "nsDTDUtils.h"
 
-
+ 
 /***************************************************************
   First, define the tagstack class
  ***************************************************************/
@@ -72,8 +72,8 @@ void nsTagStack::Empty(void) {
 void nsTagStack::Push(eHTMLTags aTag) {
 
   if(mCount>=mSize) {
-
 #ifdef _dynstack
+      //regrow the dynamic stack... 
     eHTMLTags* tmp=new eHTMLTags[2*mSize];
     nsCRT::zero(tmp,2*mSize*sizeof(eHTMLTag_html));
     nsCRT::memcpy(tmp,mTags,mSize*sizeof(eHTMLTag_html));
@@ -86,8 +86,11 @@ void nsTagStack::Push(eHTMLTags aTag) {
     delete mBits;
     mBits=tmp2;
     mSize*=2;
+#else
+    NS_PRECONDITION(mCount<eStackSize,"TagStack Overflow: DEBUG VERSION!");
 #endif
   }
+
   mTags[mCount++]=aTag;
 }
 
diff --git a/mozilla/htmlparser/src/nsIParser.h b/mozilla/htmlparser/src/nsIParser.h
index 9a7bb0bdd07..ed19cce184a 100644
--- a/mozilla/htmlparser/src/nsIParser.h
+++ b/mozilla/htmlparser/src/nsIParser.h
@@ -51,8 +51,9 @@ class nsIURL;
 enum  eParseMode {
   
   eParseMode_unknown=0,
-  eParseMode_navigator,
-  eParseMode_noquirks,
+  eParseMode_raptor,    //5.0 version of nav. and greater
+  eParseMode_navigator, //pre 5.0 versions
+  eParseMode_noquirks,  //pre 5.0 without quirks (as best as we can...)
   eParseMode_other,
   eParseMode_autodetect
 };
diff --git a/mozilla/htmlparser/src/nsParser.cpp b/mozilla/htmlparser/src/nsParser.cpp
index 2bd481a3b7a..15d063832d6 100644
--- a/mozilla/htmlparser/src/nsParser.cpp
+++ b/mozilla/htmlparser/src/nsParser.cpp
@@ -269,24 +269,6 @@ eParseMode nsParser::GetParseMode(void){
 }
 
 
-/**
- *  
- *  
- *  @update  gess 5/13/98
- *  @param   
- *  @return  
- */
-eParseMode DetermineParseMode() {
-  const char* theModeStr= PR_GetEnv("PARSE_MODE");
-  const char* other="other";
-  
-  eParseMode  result=eParseMode_navigator;
-
-  if(theModeStr) 
-    if(0==nsCRT::strcasecmp(other,theModeStr))
-      result=eParseMode_other;    
-  return result;
-}
 
 /**
  *  
@@ -357,6 +339,42 @@ eAutoDetectResult nsParser::AutoDetectContentType(nsString& aBuffer,nsString& aT
 }
 
 
+/**
+ *  This is called (by willBuildModel) when it's time to find out 
+ *  what mode the parser/DTD should run for this document.
+ *  (Each parsercontext can have it's own mode).
+ *  
+ *  @update  gess 5/13/98
+ *  @return  parsermode (define in nsIParser.h)
+ */
+eParseMode DetermineParseMode(nsParser& aParser) {
+  const char* theModeStr= PR_GetEnv("PARSE_MODE");
+  const char* other="other";
+  
+  CScanner* theScanner=aParser.GetScanner();
+  if(theScanner){
+    nsString& theBuffer=theScanner->GetBuffer();
+    PRInt32 theIndex=theBuffer.Find("HTML 4.0");
+    if(kNotFound==theIndex)
+      theIndex=theBuffer.Find("html 4.0");
+    if(kNotFound<theIndex)
+      return eParseMode_raptor;
+    else {
+      PRInt32 theIndex=theBuffer.Find("noquirks");
+      if(kNotFound==theIndex)
+        theIndex=theBuffer.Find("NOQUIRKS");
+      if(kNotFound<theIndex)
+        return eParseMode_noquirks;
+    }
+  }
+
+  if(theModeStr) 
+    if(0==nsCRT::strcasecmp(other,theModeStr))
+      return eParseMode_other;    
+  return eParseMode_navigator;
+}
+
+
 /**
  * This gets called just prior to the model actually
  * being constructed. It's important to make this the
@@ -370,17 +388,19 @@ eAutoDetectResult nsParser::AutoDetectContentType(nsString& aBuffer,nsString& aT
  */
 PRInt32 nsParser::WillBuildModel(nsString& aFilename){
 
-  mMajorIteration=-1;
-  mMinorIteration=-1;
-
-  mParserContext->mParseMode=DetermineParseMode();  
-  if(PR_TRUE==FindSuitableDTD(*mParserContext)) {
-    mParserContext->mDTD->SetParser(this);
-    mParserContext->mDTD->SetContentSink(mSink);
-    mParserContext->mDTD->WillBuildModel(aFilename,PRBool(0==mParserContext->mPrevContext));
+  mMajorIteration=-1; 
+  mMinorIteration=-1; 
+  PRInt32 result=kNoError;
+  if(mParserContext){
+    mParserContext->mParseMode=DetermineParseMode(*this);  
+    if(PR_TRUE==FindSuitableDTD(*mParserContext)) {
+      mParserContext->mDTD->SetParser(this);
+      mParserContext->mDTD->SetContentSink(mSink);
+      mParserContext->mDTD->WillBuildModel(aFilename,PRBool(0==mParserContext->mPrevContext));
+    }
   }
-
-  return kNoError;
+  else result=kInvalidParserContext;
+  return result;
 }
 
 /**
diff --git a/mozilla/htmlparser/src/nsParserTypes.h b/mozilla/htmlparser/src/nsParserTypes.h
index 2722672c50a..bbfe9c941a2 100644
--- a/mozilla/htmlparser/src/nsParserTypes.h
+++ b/mozilla/htmlparser/src/nsParserTypes.h
@@ -43,6 +43,7 @@ const PRInt32   kBadFilename      = 10004;
 const PRInt32   kBadURL           = 10005;
 const PRInt32   kInterrupted      = 10006;
 const PRInt32   kProcessComplete  = 10007;
+const PRInt32   kInvalidParserContext = 10008;
 const PRInt32   kNotFound         = -1;
 const PRInt32   kNoError          = NS_OK;
 
diff --git a/mozilla/parser/htmlparser/src/CNavDTD.cpp b/mozilla/parser/htmlparser/src/CNavDTD.cpp
index e0750f9a8b6..e43eaaeadfc 100644
--- a/mozilla/parser/htmlparser/src/CNavDTD.cpp
+++ b/mozilla/parser/htmlparser/src/CNavDTD.cpp
@@ -9,7 +9,7 @@
  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the NPL
  * for the specific language governing rights and limitations under the
  * NPL.
- *
+ * 
  * The Initial Developer of this code under the NPL is Netscape
  * Communications Corporation.  Portions created by Netscape are
  * Copyright (C) 1998 Netscape Communications Corporation.  All Rights
@@ -361,7 +361,7 @@ CNavDTD::CNavDTD() : nsIDTD(), mTokenDeque(gTokenKiller)  {
   nsCRT::zero(mTokenHandlers,sizeof(mTokenHandlers));
   mHasOpenForm=PR_FALSE;
   mHasOpenMap=PR_FALSE;
-  InitializeDefaultTokenHandlers();
+  InitializeDefaultTokenHandlers(); 
   mHeadContext=new nsDTDContext();
   mBodyContext=new nsDTDContext();
   mFormContext=0;
@@ -1905,7 +1905,13 @@ PRBool CNavDTD::CanOmit(eHTMLTags aParent,eHTMLTags aChild) const {
           result=HasOpenContainer(aChild); //don't bother if they're already open...
           break;
 
-        case eHTMLTag_button:       case eHTMLTag_fieldset:
+          //The following line was commented out to fix bug 1166. 
+          //Effectively, this allows a button to exist anywhere in the document,
+          //and not just inside a form.
+
+        //case eHTMLTag_button:       
+
+        case eHTMLTag_fieldset:
         case eHTMLTag_input:        case eHTMLTag_isindex:
         case eHTMLTag_label:        case eHTMLTag_legend:
         case eHTMLTag_select:       case eHTMLTag_textarea:
diff --git a/mozilla/parser/htmlparser/src/nsDTDUtils.cpp b/mozilla/parser/htmlparser/src/nsDTDUtils.cpp
index a3a9df7fb8e..86ac19275a3 100644
--- a/mozilla/parser/htmlparser/src/nsDTDUtils.cpp
+++ b/mozilla/parser/htmlparser/src/nsDTDUtils.cpp
@@ -19,7 +19,7 @@
 
 #include "nsDTDUtils.h"
 
-
+ 
 /***************************************************************
   First, define the tagstack class
  ***************************************************************/
@@ -72,8 +72,8 @@ void nsTagStack::Empty(void) {
 void nsTagStack::Push(eHTMLTags aTag) {
 
   if(mCount>=mSize) {
-
 #ifdef _dynstack
+      //regrow the dynamic stack... 
     eHTMLTags* tmp=new eHTMLTags[2*mSize];
     nsCRT::zero(tmp,2*mSize*sizeof(eHTMLTag_html));
     nsCRT::memcpy(tmp,mTags,mSize*sizeof(eHTMLTag_html));
@@ -86,8 +86,11 @@ void nsTagStack::Push(eHTMLTags aTag) {
     delete mBits;
     mBits=tmp2;
     mSize*=2;
+#else
+    NS_PRECONDITION(mCount<eStackSize,"TagStack Overflow: DEBUG VERSION!");
 #endif
   }
+
   mTags[mCount++]=aTag;
 }
 
diff --git a/mozilla/parser/htmlparser/src/nsIParser.h b/mozilla/parser/htmlparser/src/nsIParser.h
index 9a7bb0bdd07..ed19cce184a 100644
--- a/mozilla/parser/htmlparser/src/nsIParser.h
+++ b/mozilla/parser/htmlparser/src/nsIParser.h
@@ -51,8 +51,9 @@ class nsIURL;
 enum  eParseMode {
   
   eParseMode_unknown=0,
-  eParseMode_navigator,
-  eParseMode_noquirks,
+  eParseMode_raptor,    //5.0 version of nav. and greater
+  eParseMode_navigator, //pre 5.0 versions
+  eParseMode_noquirks,  //pre 5.0 without quirks (as best as we can...)
   eParseMode_other,
   eParseMode_autodetect
 };
diff --git a/mozilla/parser/htmlparser/src/nsParser.cpp b/mozilla/parser/htmlparser/src/nsParser.cpp
index 2bd481a3b7a..15d063832d6 100644
--- a/mozilla/parser/htmlparser/src/nsParser.cpp
+++ b/mozilla/parser/htmlparser/src/nsParser.cpp
@@ -269,24 +269,6 @@ eParseMode nsParser::GetParseMode(void){
 }
 
 
-/**
- *  
- *  
- *  @update  gess 5/13/98
- *  @param   
- *  @return  
- */
-eParseMode DetermineParseMode() {
-  const char* theModeStr= PR_GetEnv("PARSE_MODE");
-  const char* other="other";
-  
-  eParseMode  result=eParseMode_navigator;
-
-  if(theModeStr) 
-    if(0==nsCRT::strcasecmp(other,theModeStr))
-      result=eParseMode_other;    
-  return result;
-}
 
 /**
  *  
@@ -357,6 +339,42 @@ eAutoDetectResult nsParser::AutoDetectContentType(nsString& aBuffer,nsString& aT
 }
 
 
+/**
+ *  This is called (by willBuildModel) when it's time to find out 
+ *  what mode the parser/DTD should run for this document.
+ *  (Each parsercontext can have it's own mode).
+ *  
+ *  @update  gess 5/13/98
+ *  @return  parsermode (define in nsIParser.h)
+ */
+eParseMode DetermineParseMode(nsParser& aParser) {
+  const char* theModeStr= PR_GetEnv("PARSE_MODE");
+  const char* other="other";
+  
+  CScanner* theScanner=aParser.GetScanner();
+  if(theScanner){
+    nsString& theBuffer=theScanner->GetBuffer();
+    PRInt32 theIndex=theBuffer.Find("HTML 4.0");
+    if(kNotFound==theIndex)
+      theIndex=theBuffer.Find("html 4.0");
+    if(kNotFound<theIndex)
+      return eParseMode_raptor;
+    else {
+      PRInt32 theIndex=theBuffer.Find("noquirks");
+      if(kNotFound==theIndex)
+        theIndex=theBuffer.Find("NOQUIRKS");
+      if(kNotFound<theIndex)
+        return eParseMode_noquirks;
+    }
+  }
+
+  if(theModeStr) 
+    if(0==nsCRT::strcasecmp(other,theModeStr))
+      return eParseMode_other;    
+  return eParseMode_navigator;
+}
+
+
 /**
  * This gets called just prior to the model actually
  * being constructed. It's important to make this the
@@ -370,17 +388,19 @@ eAutoDetectResult nsParser::AutoDetectContentType(nsString& aBuffer,nsString& aT
  */
 PRInt32 nsParser::WillBuildModel(nsString& aFilename){
 
-  mMajorIteration=-1;
-  mMinorIteration=-1;
-
-  mParserContext->mParseMode=DetermineParseMode();  
-  if(PR_TRUE==FindSuitableDTD(*mParserContext)) {
-    mParserContext->mDTD->SetParser(this);
-    mParserContext->mDTD->SetContentSink(mSink);
-    mParserContext->mDTD->WillBuildModel(aFilename,PRBool(0==mParserContext->mPrevContext));
+  mMajorIteration=-1; 
+  mMinorIteration=-1; 
+  PRInt32 result=kNoError;
+  if(mParserContext){
+    mParserContext->mParseMode=DetermineParseMode(*this);  
+    if(PR_TRUE==FindSuitableDTD(*mParserContext)) {
+      mParserContext->mDTD->SetParser(this);
+      mParserContext->mDTD->SetContentSink(mSink);
+      mParserContext->mDTD->WillBuildModel(aFilename,PRBool(0==mParserContext->mPrevContext));
+    }
   }
-
-  return kNoError;
+  else result=kInvalidParserContext;
+  return result;
 }
 
 /**
diff --git a/mozilla/parser/htmlparser/src/nsParserTypes.h b/mozilla/parser/htmlparser/src/nsParserTypes.h
index 2722672c50a..bbfe9c941a2 100644
--- a/mozilla/parser/htmlparser/src/nsParserTypes.h
+++ b/mozilla/parser/htmlparser/src/nsParserTypes.h
@@ -43,6 +43,7 @@ const PRInt32   kBadFilename      = 10004;
 const PRInt32   kBadURL           = 10005;
 const PRInt32   kInterrupted      = 10006;
 const PRInt32   kProcessComplete  = 10007;
+const PRInt32   kInvalidParserContext = 10008;
 const PRInt32   kNotFound         = -1;
 const PRInt32   kNoError          = NS_OK;