Header manchmal verschoben

table[height="102"] {
margin: 0px auto;
}

img {
border: 0px;
}

* {
padding: 0px;
margin: 0px;
}

body {
background: #99CCFF;
color: #FFFFFF;
font-family: Arial;
font-size: 13px;
}

#header {
background:url("http://img.webme.com/pic/n/new-designs/headernewdesignsss.png") no-repeat;
height:195px;
width:663px;
top: 100px;
position: absolute;
margin-left: 384px;
}

#content {
z-index: 1;
position: absolute;
top: 282px;
width: 643px;
left: 50%;
margin-left: -290px;
background-color: #FFFFFF;
border: 1px solid #dadada;
color: #000000;
min-height: 280px;
padding: 10px 10px 10px 10px;
}

hr {
border: 1px solid #000000;
padding: 0px;
margin-bottom: 10px;
margin-top: 5px;
}

h1 {
color: #000000;
font-family: Arial;
font-size: 25px;
font-weight: bold;
}

h2 {
color: #000000;
font-family: Arial;
font-size: 15px;
font-weight: normal;
}

a {
color: #000000;
font-family: Arial;
font-size: 13px;
text-decoration: none;
font-weight: bold;
}

a:hover {
color: #dadada;
font-family: Arial;
font-size: 13px;
text-decoration: underline;
font-weight: normal;
}

textarea, input {
border: 1px solid #000000;
padding: 5px;
font-family: Arial, sans-serif;
font-size: 12px;
font-weight: bold;
background-color: #FFFFFF;
}
#selfheader {
position: absolute;
left: 50%;
top: 28px;
margin-left: -320px;}
#nav_container
{
display: none;
}
td.headline2{visibility:hidden;}