//默认处理
if(document.getElementById("Txt_Flag")!=null)
{
    if(document.getElementById("Txt_Flag").value=="")
        document.getElementById("Txt_Flag").value="default";
    shownull();
    document.getElementById("top_"+document.getElementById("Txt_Flag").value).className="present";
}
else
{
    shownull();
    document.getElementById("top_default").className="present";
}

function shownull()
{
    document.getElementById("top_default").className="";
    document.getElementById("top_movie").className="";
    document.getElementById("top_coocaak").className="";
    document.getElementById("top_teach").className="";
    document.getElementById("top_shop").className="";
    document.getElementById("top_bbs").className=""; 
}

//光标移入处理
function show(flag)
{
    shownull();
    if(flag!="")
    {
        document.getElementById("top_"+flag).className="present";
    }
    else
    {
        document.getElementById("top_default").className="present";
    }
}

//光标移出处理
function showout(flag) 
{
    if(document.getElementById("Txt_Flag").value=="")
        document.getElementById("Txt_Flag").value="default";
    shownull();
    document.getElementById("top_"+document.getElementById("Txt_Flag").value).className="present";
}