使用JavaScript定义打开网页后居中显示，并可为窗口设置大小，使用“window.open”方法打开新窗口：先来看完整的代码及调用方法：
<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
<title>打开居中的窗口</title>
<script language="javascript">
//参数-url：要打开的网站，winname：打开后的窗体名称
//参数width:打开新窗体的宽度，height：打开新窗体的高度
<!--
function openwindow( url,winName,width,height)
{
xposition=0; yposition=0;
if ((parseInt(navigator.appVersion) >= 4 ))
{
xposition = (screen.width - width) / 2;//窗体居中的x坐标
yposition = (screen.height - height) / 2;//窗体居中的y坐标
}
theproperty= "width=" + width + "," //打开窗口的属性
+ "height=" + height + ","
+ "location=0,"
+ "menubar=0,"
+ "resizable=1,"
+ "scrollbars=0,"
+ "status=0,"
+ "titlebar=0,"
+ "toolbar=0,"
+ "hotkeys=0,"
+ "screenx=" + xposition + "," //仅适用于Netscape
+ "screeny=" + yposition + ","//仅适用于Netscape
+ "left=" + xposition + ","//IE
+ "top=" + yposition;//IE
window.open( url,winName,theproperty );//打开窗口
}//-->
</script>
</head>
<body>
<a href="javascript:openwindow('http://www.google.com','openwin',300,300)">打开窗口</a>
</body>
</html>
代码的重点是设置打开窗口的一些属性，此方法的三个参数分别代表：要打开窗口的URL、打开窗口的名字、打开窗口的一些属性（如是否有滚动条、最大化按钮 等）。本例使用“(screen.width-width)/2”和“(screen.height-height)/2”获取窗体居中的坐标点，然后指 定窗体的“left”和“top”属性。