De nada!
Asi?
Código PHP:
<html>
<head>
<script>
//<!--
var intervalId=null;
var alpha = 0;
var sentido = 1;
var incremento = 5;
var velocidad = 10;
document.div_form_login = document.getElementById("div_form_login");
function visibleFormLogin(){
if(intervalId == null)
intervalId = setInterval("change_alpha()",velocidad);
}
function change_alpha()
{
alpha += (incremento * sentido);
if(navigator.userAgent.match("MSIE"))
div_form_login.filters.alpha.opacity = alpha;
else
div_form_login.style.opacity = (alpha/100).toString();
if(alpha>=100 || alpha<=0)
{
sentido = sentido==1?-1:1;
clearInterval(intervalId);
intervalId=null;
}
}
//-->
</script>
<style>
#div_form_login
{
filter: alpha(opacity=50);
background-color: red;
}
</style>
<script type="text/javascript" src="scripts/funciones.js"></script>
</head>
<body>
<a href="javascript:void(visibleFormLogin());">Login</a>
<div id="div_form_login" style="opacity: 0.0">
<form id="login-form" action="" method="post" >
<div id="div_email">
<label id="label_email" for="email">Email:</label>
<input id="email" name="email" type="text" />
</div>
<div id="div_password">
<label id="label_password" for="password">Password:</label>
<input id="password" name="password" type="password" />
</div>
<div id="submit">
<input id="entrar" name="entrar" value="Entrar" type="submit" />
</div>
</form>
</div>
</body>
</html>
Dime si te sirve
--edit--
Estoy tratando de hacer que funcione en IE (En firefox todo ok)