Set vertical scroll to top and horizontal to left:
_htmlPanel.AutoScrollPosition = new Point(_htmlPanel.HorizontalScroll.Minimum, _htmlPanel.VerticalScroll.Minimum);
Set vertical to bottom and horizontal to right:
_htmlPanel.AutoScrollPosition = new Point(_htmlPanel.HorizontalScroll.Maximum - _htmlPanel.HorizontalScroll.LargeChange, _htmlPanel.VerticalScroll.Maximum - _htmlPanel.VerticalScroll.LargeChange);
_htmlPanel.AutoScrollPosition = new Point(_htmlPanel.HorizontalScroll.Minimum, _htmlPanel.VerticalScroll.Minimum);
Set vertical to bottom and horizontal to right:
_htmlPanel.AutoScrollPosition = new Point(_htmlPanel.HorizontalScroll.Maximum - _htmlPanel.HorizontalScroll.LargeChange, _htmlPanel.VerticalScroll.Maximum - _htmlPanel.VerticalScroll.LargeChange);