function getbyid(id) {
	if (document.getElementById) {
		return document.getElementById(id);
	} else if (document.all) {
		return document.all[id];
	} else if (document.layers) {
		return document.layers[id];
	} else {
		return null;
	}
}

var isIE = navigator.userAgent.toLowerCase().indexOf('ie');


/**
 * 获取窗口的高度与宽度
 */
function getWindowSize() {
  var winWidth = 0, winHeight = 0;
  if( typeof( window.innerWidth ) == 'number' ) {
    //Non-IE
    winWidth = window.innerWidth;
    winHeight = window.innerHeight;
  } else if( document.documentElement && ( document.documentElement.clientWidth || document.documentElement.clientHeight ) ) {
    //IE 6+ in 'standards compliant mode'
    winWidth = document.documentElement.clientWidth;
    winHeight = document.documentElement.clientHeight;
  } else if( document.body && ( document.body.clientWidth || document.body.clientHeight ) ) {
    //IE 4 compatible
    winWidth = document.body.clientWidth;
    winHeight = document.body.clientHeight;
  }
  return {winWidth:winWidth,winHeight:winHeight}
}