function mychk()
{
	if(document.gbooks.username.value=="")
	{
		alert("提示：\n\n请输入您的昵称");
		document.gbooks.username.focus();
		return false;
	}
		if(document.gbooks.title.value=="")
	{
		alert("提示：\n\n请输入留言主题");
		document.gbooks.title.focus();
		return false;
	}
	if(document.gbooks.content.value=="")
	{
		alert("提示：\n\n请输入您的留言");
		document.gbooks.content.focus();
		return false;
	}
	if(document.gbooks.content.value.length>250)
	{
		alert("提示：\n\n您的留言不能超过255个字符");
		document.gbooks.content.focus();
		return false;
	}
}