问如何保持一个持久的下降状态？

EN

<html>
<head>
<script type="text/javascript">
function setSelections()
{
    document.myForm.mySelect.value = getQueryValue("mySelect");
};

function getQueryValue(key)
{
    var queryString = window.location.search.substring(1);
    var queryParams = queryString.split("&");
    for(var i = 0; i < queryParams.length; i++)
    {
        if(queryParams[i].indexOf("=") > 0)
        {
            var keyValue = queryParams[i].split("=");
            if(keyValue[0] == key)
            {
                return keyValue[1];
            }
        }
    }

    return null;
}
</script>
</head>
<body onload="setSelections();">
    <form name="myForm" action="" method="get">
        <select id="mySelect" name="mySelect" onchange="document.myForm.submit();">
            <option value="Opt1">Option 1</option>
            <option value="Opt2">Option 2</option>
            <option value="Opt3">Option 3</option>
            <option value="Opt4">Option 4</option>
        </select>
    </form>
</body>
</html>