急：在网页上的鼠标单击事件如何截获？

for example脚本说明：
第一步:把如下代码加入<body>区域中:
<SCRIPT LANGUAGE="JavaScript">
if (navigator.appName == 'Netscape')
{
document.captureEvents(Event.MOUSEMOVE);
document.onmousemove = netscapeMouseMove;
}function netscapeMouseMove(e) {
if (e.screenX != document.test.x.value && e.screenY != document.test.y.value)
{
document.test.x.value = e.screenX;
document.test.y.value = e.screenY;
}
}function micro$oftMouseMove() {
if (window.event.x != document.test.x.value && window.event.y != document.test.y.value)
{
document.test.x.value = window.event.x;
document.test.y.value = window.event.y;
}
}
</SCRIPT>
<FORM NAME="test">
X: <INPUT TYPE="TEXT" NAME="x" SIZE="4"> Y: <INPUT
TYPUE="TEXT" NAME="y" SIZE="4">
</FORM>
第二步：把<body>中内容改为：
<body bgcolor="#fef4d9" onMousemove="micro$oftMouseMove()">
window.document.onmousedown = funMouseDown;
funMouseDown() {
   alert("asdfasdfasd");
}
<HTML>
<HEAD>
<TITLE> New Document </TITLE>
<META NAME="Generator" CONTENT="EditPlus">
<META NAME="Author" CONTENT="">
<META NAME="Keywords" CONTENT="">
<META NAME="Description" CONTENT="">
</HEAD><BODY onMousedown="alert('OK')">
</BODY>
</HTML>
you can capture the mouse event "onmousedown"
and the button value is 1
onmouseover
onmouseup
onmousedown事件
<body onclick="alert('a')">