I presume you mean having the text selected so it can be removed when the user starts typing or copied to the clipboard. You cannot accomplish such thing with CSS: you need to use JavaScript:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head><title></title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<script type="text/javascript"><!--
window.onload = function(){
var t = document.getElementsByTagName("textarea");
for(var i=0, len=t.length; i<len; i++){
t[i].select();
}
}
//--></script>
</head>
<body>
<textarea>Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.</textarea>
</body>
</html>
Since you can only have one selected item at a time, it's probably more interesting to select text on focus:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head><title></title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<script type="text/javascript"><!--
window.onload = function(){
var t = document.getElementsByTagName("textarea");
for(var i=0, len=t.length; i<len; i++){
t[i].onfocus = function(e){
e.target.select();
}
}
}
//--></script>
</head>
<body>
<textarea>Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.</textarea>
<textarea>Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.</textarea>
</body>
</html>
Disclaimer: this sample code is not tested and probably buggy.
Update
Do you mean this?
textarea{
background-color: #FFEFC6;
}