把如下代码加入<body>区域中:
  <SCRIPT LANGUAGE="JavaScript">
function password() {输入正确进入密码保护页
var testV = 1;
var pass1 = prompt('请输入密码(密码是welcome):','');
while (testV < 3) {
if (!pass1) 
history.go(-1);
if (pass1 == "welcome") {
alert('密码正确!');
break;
} 
testV+=1;输入正确进入密码保护页
var pass1 = 
prompt('密码错误!请重新输入:');
}
if (pass1!="password" & testV ==3)               
history.go(-1);
return " ";
}                        
document.write(password());
</SCRIPT>输入正确进入密码保护页
 
  
        