麻烦看一下代码为什么结果不对

<!DOCTYPE html>
<html>
    <head>
        <meta charset="UTF-8">
        <title>screen</title>
        <style type="text/css">

        </style>
    </head>
    <body>
        <input type="button" onclick="availWidth()" value="当前显示屏幕宽度">
        <input type="button" onclick="avaliHeight()" value="当前显示屏幕高度">
        <input type="button" onclick="innerWidth()" value="当前窗口文档显示宽度">
        <input type="button" onclick="innerHeight()" value="当前窗口文档显示高度">
    </body>
     <script type="text/javascript">
        //补充代码
       function availWidth(){
              var w="当前显示屏幕宽度:"+screen.availWidth;
              alert(w);
       }
       function avaliHeight(){
              var w="当前显示屏幕高度:"+screen.availHeight;
              alert(w);
       }
       function innerWidth(){
              var w="当前窗口文档显示宽度"+window.innerWidth;
              alert(w);
       }
       function innerHeight(){
              var w="当前窗口文档显示高度"+window.innerHeight;
              alert(window.innerHeight);
       }
     </script>
</html>