转载地址：http://www.cnblogs.com/xiaoao808/archive/2008/07/31/1257624.html
在用户登录输入密码时，常常会有因为大写锁定开启而造成输入密码错误的情况，如果在用户大写锁定开启时给予提示，就可以尽量避免这种情况的发生。
一下是代码:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>检测大写锁定键</title>
<style type="text/css">
<!--
*{margin:0;padding:0;}
body{padding:2em;background:#242424;color:#ccc;}
h1{text-align:center;line-height:200%;}
h3{text-indent:1em;line-height:160%;color:#666;font-weight:normal;font-size:1em;}
h3 a{color:#bbb; text-decoration:none;margin:0 0.5em;}
h3 a:hover{color:#fff;}
p{margin:5em;}
span{margin:0 0.5em;font-size:85.7%;}
-->
</style>
</head>
<body>
<h1>检测大写锁定键 </h1>
<form action="#" method="post">
<p><label for="password">密码：</label><input type="password" id="password" name="password" /><span style="display:none;">大写锁定键被按下，请注意大小写</span></p>
</form>
<script type="text/javascript">
//<![CDATA[
function detectCapsLock(event){
var e = event||window.event;
var o = e.target||e.srcElement;
var oTip = o.nextSibling;
var keyCode = e.keyCode||e.which; // 按键的keyCode
var isShift = e.shiftKey ||(keyCode == 16 ) || false ; // shift键是否按住
if (
((keyCode >= 65 && keyCode <= 90 ) && !isShift) // Caps Lock 打开，且没有按住shift键
|| ((keyCode >= 97 && keyCode <= 122 ) && isShift)// Caps Lock 打开，且按住shift键
){oTip.style.display = '';}
else{oTip.style.display = 'none';}
}
document.getElementById('password').onkeypress = detectCapsLock;
//]]>
</script>
</body>
</html>