function isNumberString (InString,RefString){
	if(InString.length==0){
		return false;
	}
	for (Count=0; Count < InString.length; Count++){
		TempChar= InString.substring (Count, Count+1);
		if (RefString.indexOf (TempChar, 0)==-1)  
		return false;
	}
	return true;
}
function login_check()
{
if(document.form_mem.username.value=='')
{
alert('请输入用户名！');
document.form_mem.username.focus();
return false;
}
else
{
    if(isNumberString(document.form_mem.username.value,"1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-")!=1)
	{
			alert("[用户名]含有非法字符!");
			document.form_mem.username.focus();
			return false;
    }
}
if(document.form_mem.password.value=='')
{
alert('请输入密码！');
document.form_mem.password.focus();
return false;
}
/*if(document.form_mem.password.value.length<6||document.form_mem.password.value.length>20)
{
alert('密码必须符合6-20位字母或数字！');
document.form_mem.password.focus();
return false;
}
*/
if(document.form_mem.validcode_txt.value=='')
{
alert('请输入验证码！');
document.form_mem.validcode_txt.focus();
return false;
}
}