Thanks Daniele_ (#prototype)

a better window dimension script

getPageSize: function() {
  var xScroll, yScroll;
  var pageWidth, pageHeight;
  var viewportDimensions = document.viewport.getDimensions();
		
  if ( window.scrollMaxY ) {	
    xScroll = window.scrollMaxX;
    yScroll = window.scrollMaxY;
  } else if ( document.body.scrollHeight > viewportDimensions['height'] ){
    xScroll = document.body.scrollWidth-viewportDimensions['width'];
    yScroll = document.body.scrollHeight-viewportDimensions['height'];
  } else {
    // opera bug
    xScroll = document.body.offsetWidth;
    yScroll = document.body.offsetHeight;
  }
		
  if ( xScroll == 0 )
    pageWidth = viewportDimensions['width'];
  else
    pageWidth = viewportDimensions['width'] + xScroll;

  if ( yScroll == 0 )
    pageHeight = viewportDimensions['height'];
  else
    pageHeight = viewportDimensions['height'] + yScroll;

  return [pageWidth,pageHeight];
}