Ok this may be simple to fix, but in IE7 only (I dont have the courage to see how my site looks in IE6 aahha ) with this code

div#access_box{
width:290px;
margin:0 auto;
margin-top: 130px;
background: white;
-moz-border-radius: 5px;
border-radius: 5px;
border:2px solid #BFBFBF;
padding: 30px; 
text-shadow: 0px 1px 1px #BFBFBF;
}

div#errors_login{
position:absolute; 
top: 30px;
left: 50%;
width: 500px;
margin:0 auto;
text-align: center;
border: 1px solid red;
background: rgb(239, 44, 44); 
color:white;
font-size: 15px;
padding: 10px;
margin-left:-260px;
}


        

<div id="errors_login">

</div>";


<div id="access_box">

</div>

without errors_login everything is showed ok, with it access_box magically loses margin-top and so errors_login goes over that div! The problem seems to be position:absolute, but why? bug?