[陪你去看龙卷风]

hope it helps, it might have some bugs.
(i dont have time to debug it.)

<javascript>
function submit(){
	if((document.FORM.username.value=='SECRECTUSERNAME') && (document.FORM.password.value=='SECRECTPASSWORD')){
		location.href= "newpage.html";
	}
}
</javascript>
<form name="FORM" method="post" action="#" enctype="multipart/form-data">
Log in

Username:

<input type="text" id="username" name="username" size="15" />


Password:

<input type="password" id="password" name="password" size="15" />


<input type="button" name="login" value="Log in" onclick="submit();" /> 
</form>