function getPageHeight() {
    var windowHeight
    if (self.innerHeight) {	// all except Explorer
      windowHeight = self.innerHeight;
    } else if (document.documentElement && document.documentElement.clientHeight) { // Explorer 6 Strict Mode
      windowHeight = document.documentElement.clientHeight;
    } else if (document.body) { // other Explorers
      windowHeight = document.body.clientHeight;
    }	
    return windowHeight
}

function resizePage() {
  var height = getPageHeight();
  if (height > $("body").height()) {
     $("#float_hight").height(height - $("body").height() + 1);
  }
}
window.onresize = resizePage;