今天整理一个实例,如何用js实现弹出登录窗口:

<!doctype html>
<html>
  <head>
    <meta charset="utf-8">
    <title>弹登录框</title>
    <style>
	    #tanchuang{  (样式设置)      position: fixed;   (绝对定位)
		      top: 140px;
		      left: 415px;
		      visibility: hidden;   (默认隐藏)
		      overflow: hidden;  
		      background-color:#FFFFFF;   (背景颜色)
		      border:1px solid #878787;  (边框设置)		      border-radius:6px;  (圆角设置)
		      box-shadow:0px 5px 16px #000;  (阴影设置)
	      }
	    .tanchuang1{
		      width: 530px;
		      height: 40px;
		      border: 1px solid #ccc;
		      background: #2d2d2d;
		      border-radius:4px;
	    }
	    .denglu_1{
		      float: left;
		      position: relative;
		      top: 10px;
		      left: 16px;
	    }
	    .denglu_1 b{
		      color: #ffffff;
	    }
	    .denglu_2{
		      float: right;
		      position: relative;
		      width: 12px;
		      height: 13px;
		      background: url(wangyiyun/img/youneirong/layer.png) no-repeat 0px -93px;
		      top: 14px;
		      left: -19px;
	    }
	    .denglu_2 span{
		      color: #888888;
	    }
	    .tanchuang2{
		      width: 299px;
		      height: 208px;
		      float: left;
		      border-right: 1px dashed #ccc;
		      margin-top: 41px;
		      background: url( wangyiyun/img/youneirong/platform.png) no-repeat 45px 0px;
	    }
	    .tanchuang_input{
		      width: 225px;
		      height: 30px;
	      }
	    .tanchuangin{
		      background: #418fd9;
		      position: relative;
		      top: 130px;
		      left:33px;
		      text-align: center;
		      border-radius:3px;
		      border: 1px solid #3984ce;
	    }
	    .tanchuanginput{
		      background: #f6f6f6;
		      position: relative;
		      top: 141px;
		      left:33px;
		      border-radius:3px;
		      text-align: center;
		      border: 1px solid #c4c4c4;
	    }
	    .tanchuang3{
		      width: 228px;
		      height: 208px;
		      float: left;
		      margin-top: 40px;
	    }
	    .tanchuangnei{
		      text-decoration: none;
		      position: relative;
		      top: -39px;
		      left: 50px;
		      color: #333333;
	    }
	    .tanchuang3 li{
		      margin-top: -8px;
		      list-style-type: none;
		      font-size: 13px;
    }
	    .li1,.li3,.li2,.li4{
		      width: 41px;
		      height: 47px;
		      position: relative;
		      top: -10px;
	    }	
	    .li1{		      background: url(wangyiyun/img/logo.png) no-repeat -148px -664px;
	    }
	    .li2{
		      background: url(wangyiyun/img/logo.png) no-repeat -188px -664px;
	    }
	    .li3{
		      background: url(wangyiyun/img/logo.png) no-repeat -229px -664px;
	    }
	    .li4{
		      background: url(wangyiyun/img/logo.png) no-repeat -269px -664px;
	    }
	  </style>
</head><body>
  <div class="neishen2" onclick="showPopup(528,325)"><a href="#" ></a></div>  (内容)(定义方法showPopup(528,325))

   		  <div id="tanchuang">  (弹窗内容)
			    <div class="tanchuang1">
				      <div class="denglu_1">
					        <b>登录</b>
				      </div>	
				      <div class="denglu_2" onclick="hidePopup()">  (定义方法hidePopup())
				      </div>
			    </div>
			    <div class="tanchuang2">
				      <a href="#"><input type="button" class="tanchuang_input tanchuangin" value="手机号登录"></a>
				      <a href="#"><input type="button" class="tanchuang_input tanchuanginput" value="注册"></a>
			    </div>
			    <div class="tanchuang3">
				      <ul>
					        <li class="nnli">
						          <div  class="li1 neili"></div>
						          <a href="#" class="tanchuangnei">微信登录</a>
					        </li>
					        <li>
						          <div  class="li2 neili"></div>
						          <a href="#" class="tanchuangnei">QQ登录</a>
					        </li>
					        <li>
						          <div  class="li3 neili"></div>
						          <a href="#" class="tanchuangnei">微博登录</a>
					        </li>
					        <li>
						          <div  class="li4 neili"></div>
						          <a href="#" class="tanchuangnei">网易邮箱账号登录</a>
					        </li>
				      </ul>
			    </div>
		  </div></body>
<script  type="text/javascript" src="js/pengyou.js">
  function showPopup(w,h){   (定义方法,弹出窗口)
	    var popUp = document.getElementById("tanchuang");   (获取元素)
	    popUp.style.top = "140px";   (设置属性,弹窗距顶部高度)
	    popUp.style.left = "415px";   (设置属性,弹窗距左边宽度)
	    popUp.style.width = w + "px";   (设置属性,弹窗宽度)
	    popUp.style.height = h + "px";   (设置属性,弹窗高度)
	    popUp.style.visibility = "visible";   (设置属性,弹框窗口显示)
  }   function hidePopup(){   (定义方法,隐藏窗口)
    var popUp = document.getElementById("tanchuang"); 
    popUp.style.visibility = "hidden";   (设置窗口的隐藏属性)
  } </script>