diff --git a/htmlparser/src/nsParser.cpp b/htmlparser/src/nsParser.cpp
index 0e14f79e2bc..d7ca9fd97cd 100644
--- a/htmlparser/src/nsParser.cpp
+++ b/htmlparser/src/nsParser.cpp
@@ -424,7 +424,7 @@ eParseMode DetermineParseMode(nsParser& aParser) {
   if(theScanner){
     nsString theBufCopy;
     nsString& theBuffer=theScanner->GetBuffer();
-    theBuffer.Left(theBufCopy,300);
+    theBuffer.Left(theBufCopy,125);
     theBufCopy.ToUpperCase();
     PRInt32 theIndex=theBufCopy.Find("<!DOCTYPE");
     if(kNotFound==theIndex){
diff --git a/htmlparser/src/nsWellFormedDTD.cpp b/htmlparser/src/nsWellFormedDTD.cpp
index c84421a5ecf..c49aa4a31bd 100644
--- a/htmlparser/src/nsWellFormedDTD.cpp
+++ b/htmlparser/src/nsWellFormedDTD.cpp
@@ -184,7 +184,9 @@ eAutoDetectResult CWellFormedDTD::CanParse(nsString& aContentType, nsString& aCo
       result=eValidDetect;
     }
     else {
-      if(-1<aBuffer.Find("<?xml ")) {
+      nsAutoString temp;
+      aBuffer.Left(temp,150);  //let's only scan the first 150 or so bytes...
+      if(-1<temp.Find("<?xml ")) {
         if(0==aContentType.Length()) {
           aContentType = kXMLTextContentType; //only reset it if it's empty
         }
diff --git a/parser/htmlparser/src/nsParser.cpp b/parser/htmlparser/src/nsParser.cpp
index 0e14f79e2bc..d7ca9fd97cd 100644
--- a/parser/htmlparser/src/nsParser.cpp
+++ b/parser/htmlparser/src/nsParser.cpp
@@ -424,7 +424,7 @@ eParseMode DetermineParseMode(nsParser& aParser) {
   if(theScanner){
     nsString theBufCopy;
     nsString& theBuffer=theScanner->GetBuffer();
-    theBuffer.Left(theBufCopy,300);
+    theBuffer.Left(theBufCopy,125);
     theBufCopy.ToUpperCase();
     PRInt32 theIndex=theBufCopy.Find("<!DOCTYPE");
     if(kNotFound==theIndex){
diff --git a/parser/htmlparser/src/nsWellFormedDTD.cpp b/parser/htmlparser/src/nsWellFormedDTD.cpp
index c84421a5ecf..c49aa4a31bd 100644
--- a/parser/htmlparser/src/nsWellFormedDTD.cpp
+++ b/parser/htmlparser/src/nsWellFormedDTD.cpp
@@ -184,7 +184,9 @@ eAutoDetectResult CWellFormedDTD::CanParse(nsString& aContentType, nsString& aCo
       result=eValidDetect;
     }
     else {
-      if(-1<aBuffer.Find("<?xml ")) {
+      nsAutoString temp;
+      aBuffer.Left(temp,150);  //let's only scan the first 150 or so bytes...
+      if(-1<temp.Find("<?xml ")) {
         if(0==aContentType.Length()) {
           aContentType = kXMLTextContentType; //only reset it if it's empty
         }