function checkdata() {
 if( addform.title.value =="" ) {
alert("请输入题目")
return false;
}
if( addform.name.value =="" ) {
alert("请输入您的联系人")
return false;
}
if( addform.tel.value =="" ) {
alert("请输入您的联系电话")
return false;
} 
if( isNumberString(addform.mail.value,"1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_@.-")!=1 || addform.mail.value.length<8) {
alert("\用户注册出错，下面是产生错误的可能原因：\n\n·请输入正确的联系邮箱")
return false;
}
if( addform.content.value =="" ) {
alert("请输入您的留言内容")
return false;
} 
return true;
}
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);
}