var lastnick = "";
function checkuser()
{
    var nick = document.regform.elements['username'].value;
    if (nick == "")
	{
		document.all("usefulMsg").innerText = "请先输入用户名";
        return false;
    }

	if (nick == lastnick)
	{
        return false;
    }

    lastnick = nick;
	checkform.checkuserform.checkname.value = nick;
	document.all("usefulMsg").innerText = "检测中，请稍等...";
	checkform.checkuserform.submit();
	return true;
}