?
------解决方案--------------------
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN ">
<html>
<head>
<meta http-equiv= "pragma " content= "no-cache ">
<meta http-equiv= "Content-Type " content= "text/html; charset=gb2312 ">
<title> Document Title </title>
</head>
<body>
<input type= "text " id= "jia " value= "teststr ">
<script language= "javascript ">
var jia = document.getElementById( "jia ");
var rng = jia.createTextRange();
rng.moveStart( "character ",2);
rng.moveEnd( "character ",-2);
rng.select();
</script>
</body>
</html>