diff --git a/layout/generic/nsFrame.cpp b/layout/generic/nsFrame.cpp
index e9009c48b196..e200e031dcdc 100644
--- a/layout/generic/nsFrame.cpp
+++ b/layout/generic/nsFrame.cpp
@@ -2268,13 +2268,13 @@ nsFrame::GetNextPrevLineFromeBlockFrame(nsIPresContext* aPresContext,
   if (aOutSideLimit > 0) //start at end
     searchingLine = countLines;
   else if (aOutSideLimit <0)//start at begining
-    searchingLine = -1;//"next" will be 0
+    searchingLine = -1;//"next" will be 0  
   else 
-  if ((aPos->mDirection == eDirPrevious && searchingLine == 0) || 
-      (aPos->mDirection == eDirNext && searchingLine >= (countLines -1) )){
+    if ((aPos->mDirection == eDirPrevious && searchingLine == 0) || 
+       (aPos->mDirection == eDirNext && searchingLine >= (countLines -1) )){
       //we need to jump to new block frame.
-    return NS_ERROR_FAILURE;
-  }
+           return NS_ERROR_FAILURE;
+    }
   PRInt32 lineFrameCount;
   nsIFrame *resultFrame = nsnull;
   nsIFrame *farStoppingFrame = nsnull; //we keep searching until we find a "this" frame then we go to next line
@@ -2293,7 +2293,7 @@ nsFrame::GetNextPrevLineFromeBlockFrame(nsIPresContext* aPresContext,
     if ((aPos->mDirection == eDirPrevious && searchingLine < 0) || 
        (aPos->mDirection == eDirNext && searchingLine >= countLines ))
     {
-        //we need to jump to new block frame.
+      //we need to jump to new block frame.
       return NS_ERROR_FAILURE;
     }
     PRUint32 lineFlags;
@@ -2303,12 +2303,17 @@ nsFrame::GetNextPrevLineFromeBlockFrame(nsIPresContext* aPresContext,
       continue;
     if (NS_SUCCEEDED(result)){
       lastFrame = firstFrame;
+    if(!lastFrame)
+      return NS_ERROR_FAILURE;//XXX this is temporary, to avoid crashing
       for (;lineFrameCount > 1;lineFrameCount --){
-        result = lastFrame->GetNextSibling(&lastFrame);
+        //result = lastFrame->GetNextSibling(&lastFrame, searchingLine);
+        result = it->GetNextSibling(lastFrame, searchingLine);
         if (NS_FAILED(result)){
           NS_ASSERTION(0,"should not be reached nsFrame\n");
           continue;
         }
+        if(!lastFrame)
+          return NS_ERROR_FAILURE;
       }
       GetLastLeaf(aPresContext, &lastFrame);
 
@@ -2351,7 +2356,19 @@ nsFrame::GetNextPrevLineFromeBlockFrame(nsIPresContext* aPresContext,
         result = aPos->mTracker->GetPresContext(getter_AddRefs(context));
         nsPoint point;
         point.x = aPos->mDesiredX;
-        point.y = 0;
+        if(aPos->mDirection == eDirPrevious)
+        {
+          nsRect tempRect;
+          nsRect& tempRectRef = tempRect;
+          resultFrame->GetRect(tempRectRef);
+          nsPoint offset;
+          nsIView * view; //used for call of get offset from view
+          resultFrame->GetOffsetFromView(aPresContext, offset,&view);
+          point.y = tempRect.height + offset.y;
+        }
+        else
+          point.y = 0;
+
         result = NS_ERROR_FAILURE;
         nsIView*  view;//if frame has a view. then stop. no doubleclicking into views
         if (NS_FAILED(resultFrame->GetView(aPresContext, &view)) || !view)
diff --git a/layout/generic/nsILineIterator.h b/layout/generic/nsILineIterator.h
index 7ffc83f2e7d3..6895a9fd921a 100644
--- a/layout/generic/nsILineIterator.h
+++ b/layout/generic/nsILineIterator.h
@@ -108,6 +108,10 @@ public:
                          nsIFrame** aFrameFound,
                          PRBool* aXIsBeforeFirstFrame,
                          PRBool* aXIsAfterLastFrame) = 0;
+
+  // Give the line iterator implementor a chance todo something more complicated than
+  // nsIFrame::GetNextSibling()
+  NS_IMETHOD GetNextSibling(nsIFrame*& aFrame, PRInt32 aLineNumber) = 0;
 };
 
 #endif /* nsILineIterator_h___ */
diff --git a/layout/generic/nsLineBox.cpp b/layout/generic/nsLineBox.cpp
index ede4ae9ca908..5fbbc5e7bb1f 100644
--- a/layout/generic/nsLineBox.cpp
+++ b/layout/generic/nsLineBox.cpp
@@ -768,6 +768,12 @@ nsLineIterator::FindFrameAt(PRInt32 aLineNumber,
   return NS_OK;
 }
 
+NS_IMETHODIMP
+nsLineIterator::GetNextSibling(nsIFrame*& aFrame, PRInt32 aLineNumber)
+{
+  return aFrame->GetNextSibling(&aFrame);
+}
+
 //----------------------------------------------------------------------
 
 nsFloaterCacheList::~nsFloaterCacheList()
diff --git a/layout/generic/nsLineBox.h b/layout/generic/nsLineBox.h
index e01460eafd4c..840267dc9ca2 100644
--- a/layout/generic/nsLineBox.h
+++ b/layout/generic/nsLineBox.h
@@ -395,6 +395,8 @@ public:
                          PRBool* aXIsBeforeFirstFrame,
                          PRBool* aXIsAfterLastFrame);
 
+  NS_IMETHOD GetNextSibling(nsIFrame*& aFrame, PRInt32 aLineNumber);
+
   nsresult Init(nsLineBox* aLines, PRBool aRightToLeft);
 
 protected:
diff --git a/layout/html/base/src/nsFrame.cpp b/layout/html/base/src/nsFrame.cpp
index e9009c48b196..e200e031dcdc 100644
--- a/layout/html/base/src/nsFrame.cpp
+++ b/layout/html/base/src/nsFrame.cpp
@@ -2268,13 +2268,13 @@ nsFrame::GetNextPrevLineFromeBlockFrame(nsIPresContext* aPresContext,
   if (aOutSideLimit > 0) //start at end
     searchingLine = countLines;
   else if (aOutSideLimit <0)//start at begining
-    searchingLine = -1;//"next" will be 0
+    searchingLine = -1;//"next" will be 0  
   else 
-  if ((aPos->mDirection == eDirPrevious && searchingLine == 0) || 
-      (aPos->mDirection == eDirNext && searchingLine >= (countLines -1) )){
+    if ((aPos->mDirection == eDirPrevious && searchingLine == 0) || 
+       (aPos->mDirection == eDirNext && searchingLine >= (countLines -1) )){
       //we need to jump to new block frame.
-    return NS_ERROR_FAILURE;
-  }
+           return NS_ERROR_FAILURE;
+    }
   PRInt32 lineFrameCount;
   nsIFrame *resultFrame = nsnull;
   nsIFrame *farStoppingFrame = nsnull; //we keep searching until we find a "this" frame then we go to next line
@@ -2293,7 +2293,7 @@ nsFrame::GetNextPrevLineFromeBlockFrame(nsIPresContext* aPresContext,
     if ((aPos->mDirection == eDirPrevious && searchingLine < 0) || 
        (aPos->mDirection == eDirNext && searchingLine >= countLines ))
     {
-        //we need to jump to new block frame.
+      //we need to jump to new block frame.
       return NS_ERROR_FAILURE;
     }
     PRUint32 lineFlags;
@@ -2303,12 +2303,17 @@ nsFrame::GetNextPrevLineFromeBlockFrame(nsIPresContext* aPresContext,
       continue;
     if (NS_SUCCEEDED(result)){
       lastFrame = firstFrame;
+    if(!lastFrame)
+      return NS_ERROR_FAILURE;//XXX this is temporary, to avoid crashing
       for (;lineFrameCount > 1;lineFrameCount --){
-        result = lastFrame->GetNextSibling(&lastFrame);
+        //result = lastFrame->GetNextSibling(&lastFrame, searchingLine);
+        result = it->GetNextSibling(lastFrame, searchingLine);
         if (NS_FAILED(result)){
           NS_ASSERTION(0,"should not be reached nsFrame\n");
           continue;
         }
+        if(!lastFrame)
+          return NS_ERROR_FAILURE;
       }
       GetLastLeaf(aPresContext, &lastFrame);
 
@@ -2351,7 +2356,19 @@ nsFrame::GetNextPrevLineFromeBlockFrame(nsIPresContext* aPresContext,
         result = aPos->mTracker->GetPresContext(getter_AddRefs(context));
         nsPoint point;
         point.x = aPos->mDesiredX;
-        point.y = 0;
+        if(aPos->mDirection == eDirPrevious)
+        {
+          nsRect tempRect;
+          nsRect& tempRectRef = tempRect;
+          resultFrame->GetRect(tempRectRef);
+          nsPoint offset;
+          nsIView * view; //used for call of get offset from view
+          resultFrame->GetOffsetFromView(aPresContext, offset,&view);
+          point.y = tempRect.height + offset.y;
+        }
+        else
+          point.y = 0;
+
         result = NS_ERROR_FAILURE;
         nsIView*  view;//if frame has a view. then stop. no doubleclicking into views
         if (NS_FAILED(resultFrame->GetView(aPresContext, &view)) || !view)
diff --git a/layout/html/base/src/nsILineIterator.h b/layout/html/base/src/nsILineIterator.h
index 7ffc83f2e7d3..6895a9fd921a 100644
--- a/layout/html/base/src/nsILineIterator.h
+++ b/layout/html/base/src/nsILineIterator.h
@@ -108,6 +108,10 @@ public:
                          nsIFrame** aFrameFound,
                          PRBool* aXIsBeforeFirstFrame,
                          PRBool* aXIsAfterLastFrame) = 0;
+
+  // Give the line iterator implementor a chance todo something more complicated than
+  // nsIFrame::GetNextSibling()
+  NS_IMETHOD GetNextSibling(nsIFrame*& aFrame, PRInt32 aLineNumber) = 0;
 };
 
 #endif /* nsILineIterator_h___ */
diff --git a/layout/html/base/src/nsLineBox.cpp b/layout/html/base/src/nsLineBox.cpp
index ede4ae9ca908..5fbbc5e7bb1f 100644
--- a/layout/html/base/src/nsLineBox.cpp
+++ b/layout/html/base/src/nsLineBox.cpp
@@ -768,6 +768,12 @@ nsLineIterator::FindFrameAt(PRInt32 aLineNumber,
   return NS_OK;
 }
 
+NS_IMETHODIMP
+nsLineIterator::GetNextSibling(nsIFrame*& aFrame, PRInt32 aLineNumber)
+{
+  return aFrame->GetNextSibling(&aFrame);
+}
+
 //----------------------------------------------------------------------
 
 nsFloaterCacheList::~nsFloaterCacheList()
diff --git a/layout/html/base/src/nsLineBox.h b/layout/html/base/src/nsLineBox.h
index e01460eafd4c..840267dc9ca2 100644
--- a/layout/html/base/src/nsLineBox.h
+++ b/layout/html/base/src/nsLineBox.h
@@ -395,6 +395,8 @@ public:
                          PRBool* aXIsBeforeFirstFrame,
                          PRBool* aXIsAfterLastFrame);
 
+  NS_IMETHOD GetNextSibling(nsIFrame*& aFrame, PRInt32 aLineNumber);
+
   nsresult Init(nsLineBox* aLines, PRBool aRightToLeft);
 
 protected:
diff --git a/layout/html/table/src/nsCellMap.cpp b/layout/html/table/src/nsCellMap.cpp
index 0c0a6a0ea1a0..47a9ffd12b14 100644
--- a/layout/html/table/src/nsCellMap.cpp
+++ b/layout/html/table/src/nsCellMap.cpp
@@ -304,6 +304,20 @@ nsTableCellMap::RemoveRows(nsIPresContext* aPresContext,
   }
 }
 
+PRInt32
+nsTableCellMap::GetNumCellsOriginatingInRow(PRInt32 aRowIndex)
+{
+  PRInt32 cellCount = 0;
+  CellData* tempCell;
+  do
+  {
+	  tempCell = GetCellAt(aRowIndex,cellCount);
+	  if (tempCell)
+		  cellCount++;
+  }while(tempCell);
+  return cellCount;
+}
+
 PRInt32 
 nsTableCellMap::AppendCell(nsTableCellFrame& aCellFrame,
                            PRInt32           aRowIndex,
diff --git a/layout/html/table/src/nsCellMap.h b/layout/html/table/src/nsCellMap.h
index c1ae6101e1b6..5a25bb6b6ac4 100644
--- a/layout/html/table/src/nsCellMap.h
+++ b/layout/html/table/src/nsCellMap.h
@@ -94,7 +94,7 @@ public:
                   PRInt32         aNumRowsToRemove,
                   PRBool          aConsiderSpans);
 
-  PRInt32 GetNumCellsOriginatingInRow(PRInt32 aRowIndex) const;
+  PRInt32 GetNumCellsOriginatingInRow(PRInt32 aRowIndex);
   PRInt32 GetNumCellsOriginatingInCol(PRInt32 aColIndex) const;
 
   PRInt32 GetEffectiveRowSpan(PRInt32 aRowIndex,
diff --git a/layout/html/table/src/nsTableFrame.cpp b/layout/html/table/src/nsTableFrame.cpp
index c14220e3597b..ddd439f51c37 100644
--- a/layout/html/table/src/nsTableFrame.cpp
+++ b/layout/html/table/src/nsTableFrame.cpp
@@ -192,7 +192,8 @@ nsresult nsTableFrame::QueryInterface(const nsIID& aIID, void** aInstancePtr)
   { // note there is no addref here, frames are not addref'd
     *aInstancePtr = (void*)(nsITableLayout*)this;
     return NS_OK;
-  } else {
+  }
+  else {
     return nsHTMLContainerFrame::QueryInterface(aIID, aInstancePtr);
   }
 }
@@ -4676,3 +4677,5 @@ nsTableFrame::SizeOf(nsISizeOfHandler* aHandler, PRUint32* aResult) const
   return NS_OK;
 }
 #endif
+
+
diff --git a/layout/html/table/src/nsTableFrame.h b/layout/html/table/src/nsTableFrame.h
index 89c48a176cc0..d4724dfd978c 100644
--- a/layout/html/table/src/nsTableFrame.h
+++ b/layout/html/table/src/nsTableFrame.h
@@ -427,7 +427,7 @@ public:
 
 protected:
 
-  /** protected constructor.
+  /** protected constructor. 
     * @see NewFrame
     */
   nsTableFrame();
diff --git a/layout/html/table/src/nsTableRowGroupFrame.cpp b/layout/html/table/src/nsTableRowGroupFrame.cpp
index 4b08d56e5a46..ee0403bfac80 100644
--- a/layout/html/table/src/nsTableRowGroupFrame.cpp
+++ b/layout/html/table/src/nsTableRowGroupFrame.cpp
@@ -40,7 +40,11 @@
 #include "nsCSSRendering.h"
 #include "nsHTMLParts.h"
 
+#include "nsCellMap.h"//table cell navigation
+
 /* ----------- nsTableRowGroupFrame ---------- */
+NS_IMPL_ADDREF_INHERITED(nsTableRowGroupFrame, nsHTMLContainerFrame)
+NS_IMPL_RELEASE_INHERITED(nsTableRowGroupFrame, nsHTMLContainerFrame)
 
 nsresult
 nsTableRowGroupFrame::QueryInterface(const nsIID& aIID, void** aInstancePtr)
@@ -52,7 +56,13 @@ nsTableRowGroupFrame::QueryInterface(const nsIID& aIID, void** aInstancePtr)
   if (aIID.Equals(kITableRowGroupIID)) {
     *aInstancePtr = (void*)this;
     return NS_OK;
-  } else {
+  }
+  else if (aIID.Equals(NS_GET_IID(nsILineIterator))) 
+  { // note there is no addref here, frames are not addref'd
+    *aInstancePtr = (void*)(nsILineIterator*)this;
+    return NS_OK;
+  }
+  else {
     return nsHTMLContainerFrame::QueryInterface(aIID, aInstancePtr);
   }
 }
@@ -1641,3 +1651,178 @@ nsTableRowGroupFrame::SizeOf(nsISizeOfHandler* aHandler, PRUint32* aResult) cons
   return NS_OK;
 }
 #endif
+
+//nsILineIterator methods for nsTableFrame
+NS_IMETHODIMP
+nsTableRowGroupFrame::GetNumLines(PRInt32* aResult)
+{
+  NS_ENSURE_ARG_POINTER(aResult);
+  return GetRowCount(*aResult);
+}
+
+NS_IMETHODIMP
+nsTableRowGroupFrame::GetDirection(PRBool* aIsRightToLeft)
+{
+  NS_ENSURE_ARG_POINTER(aIsRightToLeft);
+  *aIsRightToLeft = PR_FALSE;
+  return NS_OK;
+}
+  
+NS_IMETHODIMP
+nsTableRowGroupFrame::GetLine(PRInt32 aLineNumber, nsIFrame** aFirstFrameOnLine, PRInt32* aNumFramesOnLine,
+                     nsRect& aLineBounds, PRUint32* aLineFlags)
+{
+  NS_ENSURE_ARG_POINTER(aFirstFrameOnLine);
+  NS_ENSURE_ARG_POINTER(aNumFramesOnLine);
+  NS_ENSURE_ARG_POINTER(aLineFlags);
+
+  nsIFrame* tableFrame;
+  nsTableFrame* parentFrame;
+  nsresult result = GetParent(&tableFrame);
+  if(NS_FAILED(result) || !tableFrame)
+    return result?result:NS_ERROR_FAILURE;
+
+  parentFrame = (nsTableFrame*)tableFrame;
+  nsTableCellMap* cellMap = parentFrame->GetCellMap();
+  if(!cellMap)
+     return NS_ERROR_FAILURE;
+
+  if(aLineNumber >= cellMap->GetRowCount())
+    return NS_ERROR_INVALID_ARG;
+  
+  *aLineFlags = 0;/// should we fill these in later?
+  // not gonna touch aLineBounds right now
+
+  CellData* firstCellData = cellMap->GetCellAt(aLineNumber, 0);
+  *aFirstFrameOnLine = (nsIFrame*)firstCellData->GetCellFrame();
+  *aNumFramesOnLine = cellMap->GetNumCellsOriginatingInRow(aLineNumber);
+  return NS_OK;
+}
+  
+NS_IMETHODIMP
+nsTableRowGroupFrame::FindLineContaining(nsIFrame* aFrame, PRInt32* aLineNumberResult)
+{
+  NS_ENSURE_ARG_POINTER(aFrame);
+  NS_ENSURE_ARG_POINTER(aLineNumberResult);
+
+  nsTableRowFrame* rowFrame = (nsTableRowFrame*)aFrame;
+  *aLineNumberResult = rowFrame->GetRowIndex();
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsTableRowGroupFrame::FindLineAt(nscoord aY, PRInt32* aLineNumberResult)
+{
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+  
+NS_IMETHODIMP
+nsTableRowGroupFrame::FindFrameAt(PRInt32 aLineNumber, nscoord aX, nsIFrame** aFrameFound,
+                         PRBool* aXIsBeforeFirstFrame, PRBool* aXIsAfterLastFrame)
+{
+  PRInt32 cellCount = 0;
+  CellData* cellData;
+  nsIFrame* tempFrame;
+  nsRect tempRect;
+  nsRect& tempRectRef = tempRect;
+  nsresult rv;
+
+  nsTableFrame* parentFrame;
+
+  rv = GetParent(&tempFrame);
+  if(NS_FAILED(rv) || !tempFrame)
+    return rv?rv:NS_ERROR_FAILURE;
+
+  parentFrame = (nsTableFrame*)tempFrame;
+  nsTableCellMap* cellMap = parentFrame->GetCellMap();
+  if(!cellMap)
+     return NS_ERROR_FAILURE;
+
+  cellCount = cellMap->GetNumCellsOriginatingInRow(aLineNumber);
+
+  *aXIsBeforeFirstFrame = PR_FALSE;
+  *aXIsAfterLastFrame = PR_FALSE;
+
+  for(int i =0;i < cellCount; i++)
+  {
+    cellData = cellMap->GetCellAt(aLineNumber, i);
+    tempFrame = (nsIFrame*)cellData->GetCellFrame();
+    
+    tempFrame->GetRect(tempRectRef);//offsetting x to be in row coordinates
+    if(i==0)
+    {//only do this once
+      nsRect parentRect;
+      nsRect& parentRectRef = parentRect;
+      nsIFrame* parentFrame;
+
+      rv = tempFrame->GetParent(&parentFrame);
+    
+      if(NS_FAILED(rv) || !parentFrame)
+        return rv?rv:NS_ERROR_FAILURE;
+
+      parentFrame->GetRect(parentRectRef);
+      aX -= parentRect.x;
+    }
+
+    if(aX <= 0)//short circuit for negative x coords
+    {
+      *aXIsBeforeFirstFrame = PR_TRUE;
+      *aFrameFound = tempFrame;
+      return NS_OK;
+    }
+    if(aX < (tempRect.x + tempRect.width))
+    {
+      *aFrameFound = tempFrame;
+      return NS_OK;
+    }
+  }
+  //x coord not found in frame, return last frame
+  *aXIsAfterLastFrame = PR_TRUE;
+  *aFrameFound = tempFrame;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsTableRowGroupFrame::GetNextSibling(nsIFrame*& aFrame, PRInt32 aLineNumber)
+{
+  NS_ENSURE_ARG_POINTER(aFrame);
+
+  nsITableCellLayout* cellFrame;
+  nsresult result = aFrame->QueryInterface(NS_GET_IID(nsITableCellLayout),(void**)&cellFrame);
+  
+  if(NS_FAILED(result) || !cellFrame)
+    return result?result:NS_ERROR_FAILURE;
+  
+  nsIFrame* tempFrame;
+  nsTableFrame* parentFrame;
+  nsresult rv = GetParent(&tempFrame);
+  if(NS_FAILED(rv) || !tempFrame)
+    return rv?rv:NS_ERROR_FAILURE;
+  parentFrame = (nsTableFrame*)tempFrame;
+  nsTableCellMap* cellMap = parentFrame->GetCellMap();
+  if(!cellMap)
+     return NS_ERROR_FAILURE;
+
+
+  PRInt32 colIndex;
+  PRInt32& colIndexRef = colIndex;
+  cellFrame->GetColIndex(colIndexRef);
+
+  CellData* cellData = cellMap->GetCellAt(aLineNumber, colIndex + 1);
+  
+  if(!cellData)// if this isnt a valid cell, drop down and check the next line
+  {
+    cellData = cellMap->GetCellAt(aLineNumber + 1, 0);
+    if(!cellData)
+    {
+      //*aFrame = nsnull;
+      return NS_ERROR_FAILURE;
+    }
+  }
+
+  aFrame = (nsIFrame*)cellData->GetCellFrame();
+  return NS_OK;
+}
+
+//end nsLineIterator methods
\ No newline at end of file
diff --git a/layout/html/table/src/nsTableRowGroupFrame.h b/layout/html/table/src/nsTableRowGroupFrame.h
index 267162bbf2f5..d38d653947d1 100644
--- a/layout/html/table/src/nsTableRowGroupFrame.h
+++ b/layout/html/table/src/nsTableRowGroupFrame.h
@@ -25,6 +25,7 @@
 #include "nscore.h"
 #include "nsHTMLContainerFrame.h"
 #include "nsIAtom.h"
+#include "nsILineIterator.h"
 
 class nsTableFrame;
 class nsTableRowFrame;
@@ -82,9 +83,11 @@ struct RowGroupReflowState {
  * @see nsTableFrame
  * @see nsTableRowFrame
  */
-class nsTableRowGroupFrame : public nsHTMLContainerFrame
+class nsTableRowGroupFrame : public nsHTMLContainerFrame, public nsILineIterator
 {
 public:
+  // nsISupports
+  NS_DECL_ISUPPORTS_INHERITED
 
   // default constructor supplied by the compiler
 
@@ -98,8 +101,6 @@ public:
   friend nsresult 
   NS_NewTableRowGroupFrame(nsIPresShell* aPresShell, nsIFrame** aResult);
 
-  NS_METHOD QueryInterface(const nsIID& aIID, void** aInstancePtr);
-
   NS_IMETHOD AppendFrames(nsIPresContext* aPresContext,
                           nsIPresShell&   aPresShell,
                           nsIAtom*        aListName,
@@ -195,6 +196,29 @@ public:
 
   void GetMaxElementSize(nsSize& aMaxElementSize) const;
 
+// nsILineIterator methods
+public:
+  NS_IMETHOD GetNumLines(PRInt32* aResult);
+  NS_IMETHOD GetDirection(PRBool* aIsRightToLeft);
+  
+  NS_IMETHOD GetLine(PRInt32 aLineNumber,
+                     nsIFrame** aFirstFrameOnLine,
+                     PRInt32* aNumFramesOnLine,
+                     nsRect& aLineBounds,
+                     PRUint32* aLineFlags);
+  
+  NS_IMETHOD FindLineContaining(nsIFrame* aFrame, PRInt32* aLineNumberResult);
+  NS_IMETHOD FindLineAt(nscoord aY, PRInt32* aLineNumberResult);
+  
+  NS_IMETHOD FindFrameAt(PRInt32 aLineNumber,
+                         nscoord aX,
+                         nsIFrame** aFrameFound,
+                         PRBool* aXIsBeforeFirstFrame,
+                         PRBool* aXIsAfterLastFrame);
+
+  NS_IMETHOD GetNextSibling(nsIFrame*& aFrame, PRInt32 aLineNumber);
+
+
 protected:
 
   /** implement abstract method on nsHTMLContainerFrame */
diff --git a/layout/tables/nsCellMap.cpp b/layout/tables/nsCellMap.cpp
index 0c0a6a0ea1a0..47a9ffd12b14 100644
--- a/layout/tables/nsCellMap.cpp
+++ b/layout/tables/nsCellMap.cpp
@@ -304,6 +304,20 @@ nsTableCellMap::RemoveRows(nsIPresContext* aPresContext,
   }
 }
 
+PRInt32
+nsTableCellMap::GetNumCellsOriginatingInRow(PRInt32 aRowIndex)
+{
+  PRInt32 cellCount = 0;
+  CellData* tempCell;
+  do
+  {
+	  tempCell = GetCellAt(aRowIndex,cellCount);
+	  if (tempCell)
+		  cellCount++;
+  }while(tempCell);
+  return cellCount;
+}
+
 PRInt32 
 nsTableCellMap::AppendCell(nsTableCellFrame& aCellFrame,
                            PRInt32           aRowIndex,
diff --git a/layout/tables/nsCellMap.h b/layout/tables/nsCellMap.h
index c1ae6101e1b6..5a25bb6b6ac4 100644
--- a/layout/tables/nsCellMap.h
+++ b/layout/tables/nsCellMap.h
@@ -94,7 +94,7 @@ public:
                   PRInt32         aNumRowsToRemove,
                   PRBool          aConsiderSpans);
 
-  PRInt32 GetNumCellsOriginatingInRow(PRInt32 aRowIndex) const;
+  PRInt32 GetNumCellsOriginatingInRow(PRInt32 aRowIndex);
   PRInt32 GetNumCellsOriginatingInCol(PRInt32 aColIndex) const;
 
   PRInt32 GetEffectiveRowSpan(PRInt32 aRowIndex,
diff --git a/layout/tables/nsTableFrame.cpp b/layout/tables/nsTableFrame.cpp
index c14220e3597b..ddd439f51c37 100644
--- a/layout/tables/nsTableFrame.cpp
+++ b/layout/tables/nsTableFrame.cpp
@@ -192,7 +192,8 @@ nsresult nsTableFrame::QueryInterface(const nsIID& aIID, void** aInstancePtr)
   { // note there is no addref here, frames are not addref'd
     *aInstancePtr = (void*)(nsITableLayout*)this;
     return NS_OK;
-  } else {
+  }
+  else {
     return nsHTMLContainerFrame::QueryInterface(aIID, aInstancePtr);
   }
 }
@@ -4676,3 +4677,5 @@ nsTableFrame::SizeOf(nsISizeOfHandler* aHandler, PRUint32* aResult) const
   return NS_OK;
 }
 #endif
+
+
diff --git a/layout/tables/nsTableFrame.h b/layout/tables/nsTableFrame.h
index 89c48a176cc0..d4724dfd978c 100644
--- a/layout/tables/nsTableFrame.h
+++ b/layout/tables/nsTableFrame.h
@@ -427,7 +427,7 @@ public:
 
 protected:
 
-  /** protected constructor.
+  /** protected constructor. 
     * @see NewFrame
     */
   nsTableFrame();
diff --git a/layout/tables/nsTableRowGroupFrame.cpp b/layout/tables/nsTableRowGroupFrame.cpp
index 4b08d56e5a46..ee0403bfac80 100644
--- a/layout/tables/nsTableRowGroupFrame.cpp
+++ b/layout/tables/nsTableRowGroupFrame.cpp
@@ -40,7 +40,11 @@
 #include "nsCSSRendering.h"
 #include "nsHTMLParts.h"
 
+#include "nsCellMap.h"//table cell navigation
+
 /* ----------- nsTableRowGroupFrame ---------- */
+NS_IMPL_ADDREF_INHERITED(nsTableRowGroupFrame, nsHTMLContainerFrame)
+NS_IMPL_RELEASE_INHERITED(nsTableRowGroupFrame, nsHTMLContainerFrame)
 
 nsresult
 nsTableRowGroupFrame::QueryInterface(const nsIID& aIID, void** aInstancePtr)
@@ -52,7 +56,13 @@ nsTableRowGroupFrame::QueryInterface(const nsIID& aIID, void** aInstancePtr)
   if (aIID.Equals(kITableRowGroupIID)) {
     *aInstancePtr = (void*)this;
     return NS_OK;
-  } else {
+  }
+  else if (aIID.Equals(NS_GET_IID(nsILineIterator))) 
+  { // note there is no addref here, frames are not addref'd
+    *aInstancePtr = (void*)(nsILineIterator*)this;
+    return NS_OK;
+  }
+  else {
     return nsHTMLContainerFrame::QueryInterface(aIID, aInstancePtr);
   }
 }
@@ -1641,3 +1651,178 @@ nsTableRowGroupFrame::SizeOf(nsISizeOfHandler* aHandler, PRUint32* aResult) cons
   return NS_OK;
 }
 #endif
+
+//nsILineIterator methods for nsTableFrame
+NS_IMETHODIMP
+nsTableRowGroupFrame::GetNumLines(PRInt32* aResult)
+{
+  NS_ENSURE_ARG_POINTER(aResult);
+  return GetRowCount(*aResult);
+}
+
+NS_IMETHODIMP
+nsTableRowGroupFrame::GetDirection(PRBool* aIsRightToLeft)
+{
+  NS_ENSURE_ARG_POINTER(aIsRightToLeft);
+  *aIsRightToLeft = PR_FALSE;
+  return NS_OK;
+}
+  
+NS_IMETHODIMP
+nsTableRowGroupFrame::GetLine(PRInt32 aLineNumber, nsIFrame** aFirstFrameOnLine, PRInt32* aNumFramesOnLine,
+                     nsRect& aLineBounds, PRUint32* aLineFlags)
+{
+  NS_ENSURE_ARG_POINTER(aFirstFrameOnLine);
+  NS_ENSURE_ARG_POINTER(aNumFramesOnLine);
+  NS_ENSURE_ARG_POINTER(aLineFlags);
+
+  nsIFrame* tableFrame;
+  nsTableFrame* parentFrame;
+  nsresult result = GetParent(&tableFrame);
+  if(NS_FAILED(result) || !tableFrame)
+    return result?result:NS_ERROR_FAILURE;
+
+  parentFrame = (nsTableFrame*)tableFrame;
+  nsTableCellMap* cellMap = parentFrame->GetCellMap();
+  if(!cellMap)
+     return NS_ERROR_FAILURE;
+
+  if(aLineNumber >= cellMap->GetRowCount())
+    return NS_ERROR_INVALID_ARG;
+  
+  *aLineFlags = 0;/// should we fill these in later?
+  // not gonna touch aLineBounds right now
+
+  CellData* firstCellData = cellMap->GetCellAt(aLineNumber, 0);
+  *aFirstFrameOnLine = (nsIFrame*)firstCellData->GetCellFrame();
+  *aNumFramesOnLine = cellMap->GetNumCellsOriginatingInRow(aLineNumber);
+  return NS_OK;
+}
+  
+NS_IMETHODIMP
+nsTableRowGroupFrame::FindLineContaining(nsIFrame* aFrame, PRInt32* aLineNumberResult)
+{
+  NS_ENSURE_ARG_POINTER(aFrame);
+  NS_ENSURE_ARG_POINTER(aLineNumberResult);
+
+  nsTableRowFrame* rowFrame = (nsTableRowFrame*)aFrame;
+  *aLineNumberResult = rowFrame->GetRowIndex();
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsTableRowGroupFrame::FindLineAt(nscoord aY, PRInt32* aLineNumberResult)
+{
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+  
+NS_IMETHODIMP
+nsTableRowGroupFrame::FindFrameAt(PRInt32 aLineNumber, nscoord aX, nsIFrame** aFrameFound,
+                         PRBool* aXIsBeforeFirstFrame, PRBool* aXIsAfterLastFrame)
+{
+  PRInt32 cellCount = 0;
+  CellData* cellData;
+  nsIFrame* tempFrame;
+  nsRect tempRect;
+  nsRect& tempRectRef = tempRect;
+  nsresult rv;
+
+  nsTableFrame* parentFrame;
+
+  rv = GetParent(&tempFrame);
+  if(NS_FAILED(rv) || !tempFrame)
+    return rv?rv:NS_ERROR_FAILURE;
+
+  parentFrame = (nsTableFrame*)tempFrame;
+  nsTableCellMap* cellMap = parentFrame->GetCellMap();
+  if(!cellMap)
+     return NS_ERROR_FAILURE;
+
+  cellCount = cellMap->GetNumCellsOriginatingInRow(aLineNumber);
+
+  *aXIsBeforeFirstFrame = PR_FALSE;
+  *aXIsAfterLastFrame = PR_FALSE;
+
+  for(int i =0;i < cellCount; i++)
+  {
+    cellData = cellMap->GetCellAt(aLineNumber, i);
+    tempFrame = (nsIFrame*)cellData->GetCellFrame();
+    
+    tempFrame->GetRect(tempRectRef);//offsetting x to be in row coordinates
+    if(i==0)
+    {//only do this once
+      nsRect parentRect;
+      nsRect& parentRectRef = parentRect;
+      nsIFrame* parentFrame;
+
+      rv = tempFrame->GetParent(&parentFrame);
+    
+      if(NS_FAILED(rv) || !parentFrame)
+        return rv?rv:NS_ERROR_FAILURE;
+
+      parentFrame->GetRect(parentRectRef);
+      aX -= parentRect.x;
+    }
+
+    if(aX <= 0)//short circuit for negative x coords
+    {
+      *aXIsBeforeFirstFrame = PR_TRUE;
+      *aFrameFound = tempFrame;
+      return NS_OK;
+    }
+    if(aX < (tempRect.x + tempRect.width))
+    {
+      *aFrameFound = tempFrame;
+      return NS_OK;
+    }
+  }
+  //x coord not found in frame, return last frame
+  *aXIsAfterLastFrame = PR_TRUE;
+  *aFrameFound = tempFrame;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsTableRowGroupFrame::GetNextSibling(nsIFrame*& aFrame, PRInt32 aLineNumber)
+{
+  NS_ENSURE_ARG_POINTER(aFrame);
+
+  nsITableCellLayout* cellFrame;
+  nsresult result = aFrame->QueryInterface(NS_GET_IID(nsITableCellLayout),(void**)&cellFrame);
+  
+  if(NS_FAILED(result) || !cellFrame)
+    return result?result:NS_ERROR_FAILURE;
+  
+  nsIFrame* tempFrame;
+  nsTableFrame* parentFrame;
+  nsresult rv = GetParent(&tempFrame);
+  if(NS_FAILED(rv) || !tempFrame)
+    return rv?rv:NS_ERROR_FAILURE;
+  parentFrame = (nsTableFrame*)tempFrame;
+  nsTableCellMap* cellMap = parentFrame->GetCellMap();
+  if(!cellMap)
+     return NS_ERROR_FAILURE;
+
+
+  PRInt32 colIndex;
+  PRInt32& colIndexRef = colIndex;
+  cellFrame->GetColIndex(colIndexRef);
+
+  CellData* cellData = cellMap->GetCellAt(aLineNumber, colIndex + 1);
+  
+  if(!cellData)// if this isnt a valid cell, drop down and check the next line
+  {
+    cellData = cellMap->GetCellAt(aLineNumber + 1, 0);
+    if(!cellData)
+    {
+      //*aFrame = nsnull;
+      return NS_ERROR_FAILURE;
+    }
+  }
+
+  aFrame = (nsIFrame*)cellData->GetCellFrame();
+  return NS_OK;
+}
+
+//end nsLineIterator methods
\ No newline at end of file
diff --git a/layout/tables/nsTableRowGroupFrame.h b/layout/tables/nsTableRowGroupFrame.h
index 267162bbf2f5..d38d653947d1 100644
--- a/layout/tables/nsTableRowGroupFrame.h
+++ b/layout/tables/nsTableRowGroupFrame.h
@@ -25,6 +25,7 @@
 #include "nscore.h"
 #include "nsHTMLContainerFrame.h"
 #include "nsIAtom.h"
+#include "nsILineIterator.h"
 
 class nsTableFrame;
 class nsTableRowFrame;
@@ -82,9 +83,11 @@ struct RowGroupReflowState {
  * @see nsTableFrame
  * @see nsTableRowFrame
  */
-class nsTableRowGroupFrame : public nsHTMLContainerFrame
+class nsTableRowGroupFrame : public nsHTMLContainerFrame, public nsILineIterator
 {
 public:
+  // nsISupports
+  NS_DECL_ISUPPORTS_INHERITED
 
   // default constructor supplied by the compiler
 
@@ -98,8 +101,6 @@ public:
   friend nsresult 
   NS_NewTableRowGroupFrame(nsIPresShell* aPresShell, nsIFrame** aResult);
 
-  NS_METHOD QueryInterface(const nsIID& aIID, void** aInstancePtr);
-
   NS_IMETHOD AppendFrames(nsIPresContext* aPresContext,
                           nsIPresShell&   aPresShell,
                           nsIAtom*        aListName,
@@ -195,6 +196,29 @@ public:
 
   void GetMaxElementSize(nsSize& aMaxElementSize) const;
 
+// nsILineIterator methods
+public:
+  NS_IMETHOD GetNumLines(PRInt32* aResult);
+  NS_IMETHOD GetDirection(PRBool* aIsRightToLeft);
+  
+  NS_IMETHOD GetLine(PRInt32 aLineNumber,
+                     nsIFrame** aFirstFrameOnLine,
+                     PRInt32* aNumFramesOnLine,
+                     nsRect& aLineBounds,
+                     PRUint32* aLineFlags);
+  
+  NS_IMETHOD FindLineContaining(nsIFrame* aFrame, PRInt32* aLineNumberResult);
+  NS_IMETHOD FindLineAt(nscoord aY, PRInt32* aLineNumberResult);
+  
+  NS_IMETHOD FindFrameAt(PRInt32 aLineNumber,
+                         nscoord aX,
+                         nsIFrame** aFrameFound,
+                         PRBool* aXIsBeforeFirstFrame,
+                         PRBool* aXIsAfterLastFrame);
+
+  NS_IMETHOD GetNextSibling(nsIFrame*& aFrame, PRInt32 aLineNumber);
+
+
 protected:
 
   /** implement abstract method on nsHTMLContainerFrame */