[Html/tutorial]How to make a background for your post

You can see a moving background in this post, so how can I get this ?

1) click the HTML button as the pic. has shown.

2) Put in the HTML code below

HTML code :

<div style="BACKGROUND:url(the website of your image);WIDTH:100%;HEIGHT:100%;">
<div align="center">
<div style="WIDTH:90%;HEIGHT:90%;">
<div align="center">

I learned this from ROSE BLOG
Click and check out for more !!