diff --git a/mozilla/string/obsolete/nsStr.cpp b/mozilla/string/obsolete/nsStr.cpp
index 2b65f495e23..84a6a8b21d0 100644
--- a/mozilla/string/obsolete/nsStr.cpp
+++ b/mozilla/string/obsolete/nsStr.cpp
@@ -586,7 +586,6 @@ PRInt32 nsStr::RFindCharInSet(const nsStr& aDest,const nsStr& aSet,PRBool aIgnor
   return kNotFound;
 }
 
-
 /**
  * Compare source and dest strings, up to an (optional max) number of chars
  * @param   aDest is the first str to compare
@@ -609,13 +608,39 @@ PRInt32 nsStr::Compare(const nsStr& aDest,const nsStr& aSource,PRInt32 aCount,PR
       return 1;
     }
 
-    PRInt32 maxlen=(aSource.mLength<aDest.mLength) ? aDest.mLength : aSource.mLength;
-    aCount = (aCount<0) ? maxlen : MinInt(aCount,maxlen);
+    aCount = (aCount<0) ? minlen: MinInt(aCount,minlen);
     result=(*gCompare[aDest.mCharSize][aSource.mCharSize])(aDest.mStr,aSource.mStr,aCount,aIgnoreCase);
+
+    if (0==result) {
+      if (aDest.mLength != aSource.mLength) {
+        //we think they match, but we've only compared minlen characters. 
+        //if the string lengths are different, then they don't really match.
+        result = (aDest.mLength<aSource.mLength) ? -1 : 1;
+      }
+    }
+
   }
   return result;
 }
 
+/**
+ * Overwrites the contents of dest at offset with contents of aSource
+ * 
+ * @param   aDest is the first str to compare
+ * @param   aSource is the second str to compare
+ * @param   aDestOffset is the offset within aDest where source should be copied
+ * @return  error code
+ */
+void nsStr::Overwrite(nsStr& aDest,const nsStr& aSource,PRInt32 aDestOffset) {
+  if(aDest.mLength && aSource.mLength) {
+    if((aDest.mLength-aDestOffset)>=aSource.mLength) {
+      //if you're here, then both dest and source have valid lengths
+      //and there's enough room in dest (at offset) to contain source.
+      (*gCopyChars[aSource.mCharSize][aDest.mCharSize])(aDest.mStr,aDestOffset,aSource.mStr,0,aSource.mLength);      
+    }
+  }
+}
+
 //----------------------------------------------------------------------------------------
 
 PRBool nsStr::Alloc(nsStr& aDest,PRUint32 aCount) {
diff --git a/mozilla/string/obsolete/nsStr.h b/mozilla/string/obsolete/nsStr.h
index f253391f74d..c6c7fdf11ad 100644
--- a/mozilla/string/obsolete/nsStr.h
+++ b/mozilla/string/obsolete/nsStr.h
@@ -410,6 +410,8 @@ struct NS_COM nsStr {
   static PRInt32 RFindChar(const nsStr& aDest,PRUnichar aChar, PRBool aIgnoreCase,PRInt32 anOffset);
   static PRInt32 RFindCharInSet(const nsStr& aDest,const nsStr& aSet,PRBool aIgnoreCase,PRInt32 anOffset);
 
+  static void    Overwrite(nsStr& aDest,const nsStr& aSource,PRInt32 anOffset);
+
   static PRBool   DidAcquireMemory(void);
 
   /**
diff --git a/mozilla/string/obsolete/nsString.cpp b/mozilla/string/obsolete/nsString.cpp
index aacf1443a9f..520d7e9b6f0 100644
--- a/mozilla/string/obsolete/nsString.cpp
+++ b/mozilla/string/obsolete/nsString.cpp
@@ -405,6 +405,73 @@ nsCString& nsCString::ReplaceChar(const char* aSet, PRUnichar aNewChar){
   return *this;
 }
 
+/**
+ *  This method is used to replace all occurances of the
+ *  given target with the given replacement
+ *  
+ *  @param  
+ *  @return *this 
+ */
+nsCString& nsCString::ReplaceSubstring(const char* aTarget,const char* aNewValue){
+  if(aTarget && aNewValue) {
+
+    PRInt32 len=strlen(aTarget);
+    if(0<len) {
+      CBufDescriptor theDesc1(aTarget,PR_TRUE, len+1,len);
+      nsCAutoString theTarget(theDesc1);
+
+      len=strlen(aNewValue);
+      if(0<len) {
+        CBufDescriptor theDesc2(aNewValue,PR_TRUE, len+1,len);
+        nsCAutoString theNewValue(theDesc2);
+
+        ReplaceSubstring(theTarget,theNewValue);
+      }
+    }
+  }
+  return *this;
+}
+
+/**
+ *  This method is used to replace all occurances of the
+ *  given target substring with the given replacement substring
+ *  
+ *  @param aTarget
+ *  @param aNewValue
+ *  @return *this 
+ */
+nsCString& nsCString::ReplaceSubstring(const nsCString& aTarget,const nsCString& aNewValue){
+
+
+  //WARNING: This is not working yet!!!!!
+
+  if(aTarget.mLength && aNewValue.mLength) {
+    PRBool isSameLen=(aTarget.mLength==aNewValue.mLength);
+
+    if((isSameLen) && (1==aNewValue.mLength)) {
+      ReplaceChar(aTarget.CharAt(0),aNewValue.CharAt(0));
+    }
+    else {
+      PRInt32 theIndex=0;
+      while(kNotFound!=(theIndex=nsStr::FindSubstr(*this,aTarget,PR_FALSE,theIndex))) {
+        if(aNewValue.mLength<aTarget.mLength) {
+          //Since target is longer than newValue, we should delete a few chars first, then overwrite.
+          PRInt32 theDelLen=aTarget.mLength-aNewValue.mLength;
+          nsStr::Delete(*this,theIndex,theDelLen);
+        }
+        else {
+          //this is the worst case: the newvalue is larger than the substr it's replacing
+          //so we have to insert some characters...
+          PRInt32 theInsLen=aNewValue.mLength-aTarget.mLength;
+          nsStr::Insert(*this,theIndex,aNewValue,0,theInsLen);
+        }
+        nsStr::Overwrite(*this,aNewValue,theIndex);
+      }
+    }
+  }
+  return *this;
+}
+
 /**
  *  This method is used to replace all occurances of the
  *  given source char with the given dest char
diff --git a/mozilla/string/obsolete/nsString.h b/mozilla/string/obsolete/nsString.h
index ddbbf844746..1d4cf800e73 100644
--- a/mozilla/string/obsolete/nsString.h
+++ b/mozilla/string/obsolete/nsString.h
@@ -258,6 +258,9 @@ public:
   nsCString& ReplaceChar(PRUnichar aOldChar,PRUnichar aNewChar);
   nsCString& ReplaceChar(const char* aSet,PRUnichar aNewChar);
 
+  nsCString& ReplaceSubstring(const nsCString& aTarget,const nsCString& aNewValue);
+  nsCString& ReplaceSubstring(const char* aTarget,const char* aNewValue);
+
   PRInt32 CountChar(PRUnichar aChar);
 
   /**
diff --git a/mozilla/string/obsolete/nsString2.cpp b/mozilla/string/obsolete/nsString2.cpp
index cfdc0f64231..e2444fe34ef 100644
--- a/mozilla/string/obsolete/nsString2.cpp
+++ b/mozilla/string/obsolete/nsString2.cpp
@@ -476,6 +476,72 @@ nsString& nsString::ReplaceChar(const char* aSet, PRUnichar aNewChar){
   return *this;
 }
 
+/**
+ *  This method is used to replace all occurances of the
+ *  given target with the given replacement
+ *  
+ *  @param  
+ *  @return *this 
+ */
+nsString& nsString::ReplaceSubstring(const PRUnichar* aTarget,const PRUnichar* aNewValue){
+  if(aTarget && aNewValue) {
+
+    PRInt32 len=nsCRT::strlen(aTarget);
+    if(0<len) {
+      CBufDescriptor theDesc1(aTarget,PR_TRUE, len+1,len);
+      nsAutoString theTarget(theDesc1);
+
+      len=nsCRT::strlen(aNewValue);
+      if(0<len) {
+        CBufDescriptor theDesc2(aNewValue,PR_TRUE, len+1,len);
+        nsAutoString theNewValue(theDesc2);
+
+        ReplaceSubstring(theTarget,theNewValue);
+      }
+    }
+  }
+  return *this;}
+
+/**
+ *  This method is used to replace all occurances of the
+ *  given target substring with the given replacement substring
+ *  
+ *  @param aTarget
+ *  @param aNewValue
+ *  @return *this 
+ */
+nsString& nsString::ReplaceSubstring(const nsString& aTarget,const nsString& aNewValue){
+
+
+  //WARNING: This is not working yet!!!!!
+
+  if(aTarget.mLength && aNewValue.mLength) {
+    PRBool isSameLen=(aTarget.mLength==aNewValue.mLength);
+
+    if((isSameLen) && (1==aNewValue.mLength)) {
+      ReplaceChar(aTarget.CharAt(0),aNewValue.CharAt(0));
+    }
+    else {
+      PRInt32 theIndex=0;
+      while(kNotFound!=(theIndex=nsStr::FindSubstr(*this,aTarget,PR_FALSE,theIndex))) {
+        if(aNewValue.mLength<aTarget.mLength) {
+          //Since target is longer than newValue, we should delete a few chars first, then overwrite.
+          PRInt32 theDelLen=aTarget.mLength-aNewValue.mLength;
+          nsStr::Delete(*this,theIndex,theDelLen);
+        }
+        else {
+          //this is the worst case: the newvalue is larger than the substr it's replacing
+          //so we have to insert some characters...
+          PRInt32 theInsLen=aNewValue.mLength-aTarget.mLength;
+          nsStr::Insert(*this,theIndex,aNewValue,0,theInsLen);
+        }
+        nsStr::Overwrite(*this,aNewValue,theIndex);
+      }
+    }
+  }
+  return *this;
+}
+
 /**
  *  This method is used to replace all occurances of the
  *  given source char with the given dest char
diff --git a/mozilla/string/obsolete/nsString2.h b/mozilla/string/obsolete/nsString2.h
index c9c8f53a67b..6c6d5798ac0 100644
--- a/mozilla/string/obsolete/nsString2.h
+++ b/mozilla/string/obsolete/nsString2.h
@@ -297,6 +297,9 @@ public:
   nsString& ReplaceChar(PRUnichar anOldChar,PRUnichar aNewChar);
   nsString& ReplaceChar(const char* aSet,PRUnichar aNewChar);
 
+  nsString& ReplaceSubstring(const nsString& aTarget,const nsString& aNewValue);
+  nsString& ReplaceSubstring(const PRUnichar* aTarget,const PRUnichar* aNewValue);
+
   PRInt32 CountChar(PRUnichar aChar);
 
   /**
diff --git a/mozilla/xpcom/ds/nsCRT.h b/mozilla/xpcom/ds/nsCRT.h
index 1196877570f..ff48ae00ba4 100644
--- a/mozilla/xpcom/ds/nsCRT.h
+++ b/mozilla/xpcom/ds/nsCRT.h
@@ -144,7 +144,12 @@ public:
 
   /// Case-insensitive string comparison with length
   static PRInt32 strncasecmp(const char* s1, const char* s2, PRUint32 aMaxLen) {
-    return PRInt32(PL_strncasecmp(s1, s2, aMaxLen));
+    PRInt32 result=PRInt32(PL_strncasecmp(s1, s2, aMaxLen));
+    //Egags. PL_strncasecmp is returning *very* negative numbers.
+    //Some folks expect -1,0,1, so let's temper it's enthusiasm.
+    if(result<0) 
+      result=-1;
+    return result;
   }
 
   static PRInt32 strncmp(const char* s1, const char* s2, PRInt32 aMaxLen) {
diff --git a/mozilla/xpcom/ds/nsStr.cpp b/mozilla/xpcom/ds/nsStr.cpp
index 2b65f495e23..84a6a8b21d0 100644
--- a/mozilla/xpcom/ds/nsStr.cpp
+++ b/mozilla/xpcom/ds/nsStr.cpp
@@ -586,7 +586,6 @@ PRInt32 nsStr::RFindCharInSet(const nsStr& aDest,const nsStr& aSet,PRBool aIgnor
   return kNotFound;
 }
 
-
 /**
  * Compare source and dest strings, up to an (optional max) number of chars
  * @param   aDest is the first str to compare
@@ -609,13 +608,39 @@ PRInt32 nsStr::Compare(const nsStr& aDest,const nsStr& aSource,PRInt32 aCount,PR
       return 1;
     }
 
-    PRInt32 maxlen=(aSource.mLength<aDest.mLength) ? aDest.mLength : aSource.mLength;
-    aCount = (aCount<0) ? maxlen : MinInt(aCount,maxlen);
+    aCount = (aCount<0) ? minlen: MinInt(aCount,minlen);
     result=(*gCompare[aDest.mCharSize][aSource.mCharSize])(aDest.mStr,aSource.mStr,aCount,aIgnoreCase);
+
+    if (0==result) {
+      if (aDest.mLength != aSource.mLength) {
+        //we think they match, but we've only compared minlen characters. 
+        //if the string lengths are different, then they don't really match.
+        result = (aDest.mLength<aSource.mLength) ? -1 : 1;
+      }
+    }
+
   }
   return result;
 }
 
+/**
+ * Overwrites the contents of dest at offset with contents of aSource
+ * 
+ * @param   aDest is the first str to compare
+ * @param   aSource is the second str to compare
+ * @param   aDestOffset is the offset within aDest where source should be copied
+ * @return  error code
+ */
+void nsStr::Overwrite(nsStr& aDest,const nsStr& aSource,PRInt32 aDestOffset) {
+  if(aDest.mLength && aSource.mLength) {
+    if((aDest.mLength-aDestOffset)>=aSource.mLength) {
+      //if you're here, then both dest and source have valid lengths
+      //and there's enough room in dest (at offset) to contain source.
+      (*gCopyChars[aSource.mCharSize][aDest.mCharSize])(aDest.mStr,aDestOffset,aSource.mStr,0,aSource.mLength);      
+    }
+  }
+}
+
 //----------------------------------------------------------------------------------------
 
 PRBool nsStr::Alloc(nsStr& aDest,PRUint32 aCount) {
diff --git a/mozilla/xpcom/ds/nsStr.h b/mozilla/xpcom/ds/nsStr.h
index f253391f74d..c6c7fdf11ad 100644
--- a/mozilla/xpcom/ds/nsStr.h
+++ b/mozilla/xpcom/ds/nsStr.h
@@ -410,6 +410,8 @@ struct NS_COM nsStr {
   static PRInt32 RFindChar(const nsStr& aDest,PRUnichar aChar, PRBool aIgnoreCase,PRInt32 anOffset);
   static PRInt32 RFindCharInSet(const nsStr& aDest,const nsStr& aSet,PRBool aIgnoreCase,PRInt32 anOffset);
 
+  static void    Overwrite(nsStr& aDest,const nsStr& aSource,PRInt32 anOffset);
+
   static PRBool   DidAcquireMemory(void);
 
   /**
diff --git a/mozilla/xpcom/ds/nsString.cpp b/mozilla/xpcom/ds/nsString.cpp
index aacf1443a9f..520d7e9b6f0 100644
--- a/mozilla/xpcom/ds/nsString.cpp
+++ b/mozilla/xpcom/ds/nsString.cpp
@@ -405,6 +405,73 @@ nsCString& nsCString::ReplaceChar(const char* aSet, PRUnichar aNewChar){
   return *this;
 }
 
+/**
+ *  This method is used to replace all occurances of the
+ *  given target with the given replacement
+ *  
+ *  @param  
+ *  @return *this 
+ */
+nsCString& nsCString::ReplaceSubstring(const char* aTarget,const char* aNewValue){
+  if(aTarget && aNewValue) {
+
+    PRInt32 len=strlen(aTarget);
+    if(0<len) {
+      CBufDescriptor theDesc1(aTarget,PR_TRUE, len+1,len);
+      nsCAutoString theTarget(theDesc1);
+
+      len=strlen(aNewValue);
+      if(0<len) {
+        CBufDescriptor theDesc2(aNewValue,PR_TRUE, len+1,len);
+        nsCAutoString theNewValue(theDesc2);
+
+        ReplaceSubstring(theTarget,theNewValue);
+      }
+    }
+  }
+  return *this;
+}
+
+/**
+ *  This method is used to replace all occurances of the
+ *  given target substring with the given replacement substring
+ *  
+ *  @param aTarget
+ *  @param aNewValue
+ *  @return *this 
+ */
+nsCString& nsCString::ReplaceSubstring(const nsCString& aTarget,const nsCString& aNewValue){
+
+
+  //WARNING: This is not working yet!!!!!
+
+  if(aTarget.mLength && aNewValue.mLength) {
+    PRBool isSameLen=(aTarget.mLength==aNewValue.mLength);
+
+    if((isSameLen) && (1==aNewValue.mLength)) {
+      ReplaceChar(aTarget.CharAt(0),aNewValue.CharAt(0));
+    }
+    else {
+      PRInt32 theIndex=0;
+      while(kNotFound!=(theIndex=nsStr::FindSubstr(*this,aTarget,PR_FALSE,theIndex))) {
+        if(aNewValue.mLength<aTarget.mLength) {
+          //Since target is longer than newValue, we should delete a few chars first, then overwrite.
+          PRInt32 theDelLen=aTarget.mLength-aNewValue.mLength;
+          nsStr::Delete(*this,theIndex,theDelLen);
+        }
+        else {
+          //this is the worst case: the newvalue is larger than the substr it's replacing
+          //so we have to insert some characters...
+          PRInt32 theInsLen=aNewValue.mLength-aTarget.mLength;
+          nsStr::Insert(*this,theIndex,aNewValue,0,theInsLen);
+        }
+        nsStr::Overwrite(*this,aNewValue,theIndex);
+      }
+    }
+  }
+  return *this;
+}
+
 /**
  *  This method is used to replace all occurances of the
  *  given source char with the given dest char
diff --git a/mozilla/xpcom/ds/nsString.h b/mozilla/xpcom/ds/nsString.h
index ddbbf844746..1d4cf800e73 100644
--- a/mozilla/xpcom/ds/nsString.h
+++ b/mozilla/xpcom/ds/nsString.h
@@ -258,6 +258,9 @@ public:
   nsCString& ReplaceChar(PRUnichar aOldChar,PRUnichar aNewChar);
   nsCString& ReplaceChar(const char* aSet,PRUnichar aNewChar);
 
+  nsCString& ReplaceSubstring(const nsCString& aTarget,const nsCString& aNewValue);
+  nsCString& ReplaceSubstring(const char* aTarget,const char* aNewValue);
+
   PRInt32 CountChar(PRUnichar aChar);
 
   /**
diff --git a/mozilla/xpcom/ds/nsString2.cpp b/mozilla/xpcom/ds/nsString2.cpp
index cfdc0f64231..e2444fe34ef 100644
--- a/mozilla/xpcom/ds/nsString2.cpp
+++ b/mozilla/xpcom/ds/nsString2.cpp
@@ -476,6 +476,72 @@ nsString& nsString::ReplaceChar(const char* aSet, PRUnichar aNewChar){
   return *this;
 }
 
+/**
+ *  This method is used to replace all occurances of the
+ *  given target with the given replacement
+ *  
+ *  @param  
+ *  @return *this 
+ */
+nsString& nsString::ReplaceSubstring(const PRUnichar* aTarget,const PRUnichar* aNewValue){
+  if(aTarget && aNewValue) {
+
+    PRInt32 len=nsCRT::strlen(aTarget);
+    if(0<len) {
+      CBufDescriptor theDesc1(aTarget,PR_TRUE, len+1,len);
+      nsAutoString theTarget(theDesc1);
+
+      len=nsCRT::strlen(aNewValue);
+      if(0<len) {
+        CBufDescriptor theDesc2(aNewValue,PR_TRUE, len+1,len);
+        nsAutoString theNewValue(theDesc2);
+
+        ReplaceSubstring(theTarget,theNewValue);
+      }
+    }
+  }
+  return *this;}
+
+/**
+ *  This method is used to replace all occurances of the
+ *  given target substring with the given replacement substring
+ *  
+ *  @param aTarget
+ *  @param aNewValue
+ *  @return *this 
+ */
+nsString& nsString::ReplaceSubstring(const nsString& aTarget,const nsString& aNewValue){
+
+
+  //WARNING: This is not working yet!!!!!
+
+  if(aTarget.mLength && aNewValue.mLength) {
+    PRBool isSameLen=(aTarget.mLength==aNewValue.mLength);
+
+    if((isSameLen) && (1==aNewValue.mLength)) {
+      ReplaceChar(aTarget.CharAt(0),aNewValue.CharAt(0));
+    }
+    else {
+      PRInt32 theIndex=0;
+      while(kNotFound!=(theIndex=nsStr::FindSubstr(*this,aTarget,PR_FALSE,theIndex))) {
+        if(aNewValue.mLength<aTarget.mLength) {
+          //Since target is longer than newValue, we should delete a few chars first, then overwrite.
+          PRInt32 theDelLen=aTarget.mLength-aNewValue.mLength;
+          nsStr::Delete(*this,theIndex,theDelLen);
+        }
+        else {
+          //this is the worst case: the newvalue is larger than the substr it's replacing
+          //so we have to insert some characters...
+          PRInt32 theInsLen=aNewValue.mLength-aTarget.mLength;
+          nsStr::Insert(*this,theIndex,aNewValue,0,theInsLen);
+        }
+        nsStr::Overwrite(*this,aNewValue,theIndex);
+      }
+    }
+  }
+  return *this;
+}
+
 /**
  *  This method is used to replace all occurances of the
  *  given source char with the given dest char
diff --git a/mozilla/xpcom/ds/nsString2.h b/mozilla/xpcom/ds/nsString2.h
index c9c8f53a67b..6c6d5798ac0 100644
--- a/mozilla/xpcom/ds/nsString2.h
+++ b/mozilla/xpcom/ds/nsString2.h
@@ -297,6 +297,9 @@ public:
   nsString& ReplaceChar(PRUnichar anOldChar,PRUnichar aNewChar);
   nsString& ReplaceChar(const char* aSet,PRUnichar aNewChar);
 
+  nsString& ReplaceSubstring(const nsString& aTarget,const nsString& aNewValue);
+  nsString& ReplaceSubstring(const PRUnichar* aTarget,const PRUnichar* aNewValue);
+
   PRInt32 CountChar(PRUnichar aChar);
 
   /**
diff --git a/mozilla/xpcom/string/obsolete/nsStr.cpp b/mozilla/xpcom/string/obsolete/nsStr.cpp
index 2b65f495e23..84a6a8b21d0 100644
--- a/mozilla/xpcom/string/obsolete/nsStr.cpp
+++ b/mozilla/xpcom/string/obsolete/nsStr.cpp
@@ -586,7 +586,6 @@ PRInt32 nsStr::RFindCharInSet(const nsStr& aDest,const nsStr& aSet,PRBool aIgnor
   return kNotFound;
 }
 
-
 /**
  * Compare source and dest strings, up to an (optional max) number of chars
  * @param   aDest is the first str to compare
@@ -609,13 +608,39 @@ PRInt32 nsStr::Compare(const nsStr& aDest,const nsStr& aSource,PRInt32 aCount,PR
       return 1;
     }
 
-    PRInt32 maxlen=(aSource.mLength<aDest.mLength) ? aDest.mLength : aSource.mLength;
-    aCount = (aCount<0) ? maxlen : MinInt(aCount,maxlen);
+    aCount = (aCount<0) ? minlen: MinInt(aCount,minlen);
     result=(*gCompare[aDest.mCharSize][aSource.mCharSize])(aDest.mStr,aSource.mStr,aCount,aIgnoreCase);
+
+    if (0==result) {
+      if (aDest.mLength != aSource.mLength) {
+        //we think they match, but we've only compared minlen characters. 
+        //if the string lengths are different, then they don't really match.
+        result = (aDest.mLength<aSource.mLength) ? -1 : 1;
+      }
+    }
+
   }
   return result;
 }
 
+/**
+ * Overwrites the contents of dest at offset with contents of aSource
+ * 
+ * @param   aDest is the first str to compare
+ * @param   aSource is the second str to compare
+ * @param   aDestOffset is the offset within aDest where source should be copied
+ * @return  error code
+ */
+void nsStr::Overwrite(nsStr& aDest,const nsStr& aSource,PRInt32 aDestOffset) {
+  if(aDest.mLength && aSource.mLength) {
+    if((aDest.mLength-aDestOffset)>=aSource.mLength) {
+      //if you're here, then both dest and source have valid lengths
+      //and there's enough room in dest (at offset) to contain source.
+      (*gCopyChars[aSource.mCharSize][aDest.mCharSize])(aDest.mStr,aDestOffset,aSource.mStr,0,aSource.mLength);      
+    }
+  }
+}
+
 //----------------------------------------------------------------------------------------
 
 PRBool nsStr::Alloc(nsStr& aDest,PRUint32 aCount) {
diff --git a/mozilla/xpcom/string/obsolete/nsStr.h b/mozilla/xpcom/string/obsolete/nsStr.h
index f253391f74d..c6c7fdf11ad 100644
--- a/mozilla/xpcom/string/obsolete/nsStr.h
+++ b/mozilla/xpcom/string/obsolete/nsStr.h
@@ -410,6 +410,8 @@ struct NS_COM nsStr {
   static PRInt32 RFindChar(const nsStr& aDest,PRUnichar aChar, PRBool aIgnoreCase,PRInt32 anOffset);
   static PRInt32 RFindCharInSet(const nsStr& aDest,const nsStr& aSet,PRBool aIgnoreCase,PRInt32 anOffset);
 
+  static void    Overwrite(nsStr& aDest,const nsStr& aSource,PRInt32 anOffset);
+
   static PRBool   DidAcquireMemory(void);
 
   /**
diff --git a/mozilla/xpcom/string/obsolete/nsString.cpp b/mozilla/xpcom/string/obsolete/nsString.cpp
index aacf1443a9f..520d7e9b6f0 100644
--- a/mozilla/xpcom/string/obsolete/nsString.cpp
+++ b/mozilla/xpcom/string/obsolete/nsString.cpp
@@ -405,6 +405,73 @@ nsCString& nsCString::ReplaceChar(const char* aSet, PRUnichar aNewChar){
   return *this;
 }
 
+/**
+ *  This method is used to replace all occurances of the
+ *  given target with the given replacement
+ *  
+ *  @param  
+ *  @return *this 
+ */
+nsCString& nsCString::ReplaceSubstring(const char* aTarget,const char* aNewValue){
+  if(aTarget && aNewValue) {
+
+    PRInt32 len=strlen(aTarget);
+    if(0<len) {
+      CBufDescriptor theDesc1(aTarget,PR_TRUE, len+1,len);
+      nsCAutoString theTarget(theDesc1);
+
+      len=strlen(aNewValue);
+      if(0<len) {
+        CBufDescriptor theDesc2(aNewValue,PR_TRUE, len+1,len);
+        nsCAutoString theNewValue(theDesc2);
+
+        ReplaceSubstring(theTarget,theNewValue);
+      }
+    }
+  }
+  return *this;
+}
+
+/**
+ *  This method is used to replace all occurances of the
+ *  given target substring with the given replacement substring
+ *  
+ *  @param aTarget
+ *  @param aNewValue
+ *  @return *this 
+ */
+nsCString& nsCString::ReplaceSubstring(const nsCString& aTarget,const nsCString& aNewValue){
+
+
+  //WARNING: This is not working yet!!!!!
+
+  if(aTarget.mLength && aNewValue.mLength) {
+    PRBool isSameLen=(aTarget.mLength==aNewValue.mLength);
+
+    if((isSameLen) && (1==aNewValue.mLength)) {
+      ReplaceChar(aTarget.CharAt(0),aNewValue.CharAt(0));
+    }
+    else {
+      PRInt32 theIndex=0;
+      while(kNotFound!=(theIndex=nsStr::FindSubstr(*this,aTarget,PR_FALSE,theIndex))) {
+        if(aNewValue.mLength<aTarget.mLength) {
+          //Since target is longer than newValue, we should delete a few chars first, then overwrite.
+          PRInt32 theDelLen=aTarget.mLength-aNewValue.mLength;
+          nsStr::Delete(*this,theIndex,theDelLen);
+        }
+        else {
+          //this is the worst case: the newvalue is larger than the substr it's replacing
+          //so we have to insert some characters...
+          PRInt32 theInsLen=aNewValue.mLength-aTarget.mLength;
+          nsStr::Insert(*this,theIndex,aNewValue,0,theInsLen);
+        }
+        nsStr::Overwrite(*this,aNewValue,theIndex);
+      }
+    }
+  }
+  return *this;
+}
+
 /**
  *  This method is used to replace all occurances of the
  *  given source char with the given dest char
diff --git a/mozilla/xpcom/string/obsolete/nsString.h b/mozilla/xpcom/string/obsolete/nsString.h
index ddbbf844746..1d4cf800e73 100644
--- a/mozilla/xpcom/string/obsolete/nsString.h
+++ b/mozilla/xpcom/string/obsolete/nsString.h
@@ -258,6 +258,9 @@ public:
   nsCString& ReplaceChar(PRUnichar aOldChar,PRUnichar aNewChar);
   nsCString& ReplaceChar(const char* aSet,PRUnichar aNewChar);
 
+  nsCString& ReplaceSubstring(const nsCString& aTarget,const nsCString& aNewValue);
+  nsCString& ReplaceSubstring(const char* aTarget,const char* aNewValue);
+
   PRInt32 CountChar(PRUnichar aChar);
 
   /**
diff --git a/mozilla/xpcom/string/obsolete/nsString2.cpp b/mozilla/xpcom/string/obsolete/nsString2.cpp
index cfdc0f64231..e2444fe34ef 100644
--- a/mozilla/xpcom/string/obsolete/nsString2.cpp
+++ b/mozilla/xpcom/string/obsolete/nsString2.cpp
@@ -476,6 +476,72 @@ nsString& nsString::ReplaceChar(const char* aSet, PRUnichar aNewChar){
   return *this;
 }
 
+/**
+ *  This method is used to replace all occurances of the
+ *  given target with the given replacement
+ *  
+ *  @param  
+ *  @return *this 
+ */
+nsString& nsString::ReplaceSubstring(const PRUnichar* aTarget,const PRUnichar* aNewValue){
+  if(aTarget && aNewValue) {
+
+    PRInt32 len=nsCRT::strlen(aTarget);
+    if(0<len) {
+      CBufDescriptor theDesc1(aTarget,PR_TRUE, len+1,len);
+      nsAutoString theTarget(theDesc1);
+
+      len=nsCRT::strlen(aNewValue);
+      if(0<len) {
+        CBufDescriptor theDesc2(aNewValue,PR_TRUE, len+1,len);
+        nsAutoString theNewValue(theDesc2);
+
+        ReplaceSubstring(theTarget,theNewValue);
+      }
+    }
+  }
+  return *this;}
+
+/**
+ *  This method is used to replace all occurances of the
+ *  given target substring with the given replacement substring
+ *  
+ *  @param aTarget
+ *  @param aNewValue
+ *  @return *this 
+ */
+nsString& nsString::ReplaceSubstring(const nsString& aTarget,const nsString& aNewValue){
+
+
+  //WARNING: This is not working yet!!!!!
+
+  if(aTarget.mLength && aNewValue.mLength) {
+    PRBool isSameLen=(aTarget.mLength==aNewValue.mLength);
+
+    if((isSameLen) && (1==aNewValue.mLength)) {
+      ReplaceChar(aTarget.CharAt(0),aNewValue.CharAt(0));
+    }
+    else {
+      PRInt32 theIndex=0;
+      while(kNotFound!=(theIndex=nsStr::FindSubstr(*this,aTarget,PR_FALSE,theIndex))) {
+        if(aNewValue.mLength<aTarget.mLength) {
+          //Since target is longer than newValue, we should delete a few chars first, then overwrite.
+          PRInt32 theDelLen=aTarget.mLength-aNewValue.mLength;
+          nsStr::Delete(*this,theIndex,theDelLen);
+        }
+        else {
+          //this is the worst case: the newvalue is larger than the substr it's replacing
+          //so we have to insert some characters...
+          PRInt32 theInsLen=aNewValue.mLength-aTarget.mLength;
+          nsStr::Insert(*this,theIndex,aNewValue,0,theInsLen);
+        }
+        nsStr::Overwrite(*this,aNewValue,theIndex);
+      }
+    }
+  }
+  return *this;
+}
+
 /**
  *  This method is used to replace all occurances of the
  *  given source char with the given dest char
diff --git a/mozilla/xpcom/string/obsolete/nsString2.h b/mozilla/xpcom/string/obsolete/nsString2.h
index c9c8f53a67b..6c6d5798ac0 100644
--- a/mozilla/xpcom/string/obsolete/nsString2.h
+++ b/mozilla/xpcom/string/obsolete/nsString2.h
@@ -297,6 +297,9 @@ public:
   nsString& ReplaceChar(PRUnichar anOldChar,PRUnichar aNewChar);
   nsString& ReplaceChar(const char* aSet,PRUnichar aNewChar);
 
+  nsString& ReplaceSubstring(const nsString& aTarget,const nsString& aNewValue);
+  nsString& ReplaceSubstring(const PRUnichar* aTarget,const PRUnichar* aNewValue);
+
   PRInt32 CountChar(PRUnichar aChar);
 
   /**