<html>	<head>		<title>错误处理</title>		<script language="javascript" type="text/javascript">			<!--				window.onerror = showErr;				function showErr(errMessage,errUrl,errLine) 				{ 					var str = "JavaScript程序出错:\n"					str += "错误信息:" + errMessage + "\n";					str += "产生错误的文件:" + errUrl + "\n";					str += "产生错误的行数:" + errLine + "\n";					alert(str);					return true;				}				//以下是一个错误语句,因为变量a和b都没有定义。				var err = a*b;			-->		</script>	</head>	<body>	</body></html>