html entities changed to html tag automaticly

hi,I am using fckeditor 2.5.1 build 17566 with asp.net 2.0 and windows server 2003.
when I try to input some html tag in editor,the html code such as < and > and & will be changed to html entities automaticly.
that's right.
but after I post the form, all the html tag will be changed to real html tag, that's not the way that I want.
ie.

1.input string like this:

this is html code <b>hi</b>

2.see in the "source" model, the string will be changed to be this:

<p>this is html code &lt;b&gt;hi&lt;/b&gt;</p>

3.after post, the string will be changd to be this:

<p>this is html code <b>hi</b></p>

I want to keep the string be the final result, witch contains html entities:

<p>this is html code &lt;b&gt;hi&lt;/b&gt;</p>

anyone reply will be apreciated.