text: //author:caibaojian
  //website:http://caibaojian.com
  //weibo:http:weibo.com/kujian
  //兼容UC竖屏转横屏出现的BUG
  //自定义设计稿的宽度：designWidth
  //最大宽度:maxWidth
  ;(function(designWidth, maxWidth) {
  	var doc = document,
  	win = window,
  	docEl = doc.documentElement,
  	remStyle = document.createElement("style"),
  	tid;
  
  	function refreshRem() {
  		var width = docEl.getBoundingClientRect().width;
  		maxWidth = maxWidth || 540;
  		width>maxWidth && (width=maxWidth);
  		var rem = width * 100 / designWidth;
  		remStyle.innerHTML = 'html{font-size:' + rem + 'px;}';
  	}
  
  	if (docEl.firstElementChild) {
  		docEl.firstElementChild.appendChild(remStyle);
  	} else {
  		var wrap = doc.createElement("div");
  		wrap.appendChild(remStyle);
  		doc.write(wrap.innerHTML);
  		wrap = null;
  	}
  	//要等 wiewport 设置好后才能执行 refreshRem，不然 refreshRem 会执行2次；
  	refreshRem();
  
  	win.addEventListener("resize", function() {
  		clearTimeout(tid); //防止执行两次
  		tid = setTimeout(refreshRem, 300);
  	}, false);
  
  	win.addEventListener("pageshow", function(e) {
  		if (e.persisted) { // 浏览器后退的时候重新计算
  			clearTimeout(tid);
  			tid = setTimeout(refreshRem, 300);
  		}
  	}, false);
  
  	if (doc.readyState === "complete") {
  		doc.body.style.fontSize = "16px";
  	} else {
  		doc.addEventListener("DOMContentLoaded", function(e) {
  			doc.body.style.fontSize = "16px";
  		}, false);
  	}
  })(750, 750);