hi ,i am chinese,it 's nice to meet you!
first,you need not to write another DIV tags to show your backgroud image,
sorry,I am English is poor,i dot know to express it,but I can write it,if you have another questions,please email to me ,myemail
zhu520@qq.com
<!-- Header -->
<center>
<div align="center" id="header" style=" height:500px;background-image:url(
http://img775.ph.126.net/_xXw0DIqYPwUD2 ... 038224.jpg)"> <font size="6" color="#FF0000" face="Times New Roman">My Page</font></div>
</center>
<!-- Header -->