how to change the image baground blog undefined

1. log in blogs

2.menu layout

3.edit html

4.input this code in css
replace the yellow with the image url you like

body {
background:#fff

url('http://www.yenta4.com/webboard/upload_images/301219_2931963.jpg');

margin:0;
padding:40px 20px;
font:x-small Georgia,Serif;
text-align:center;
color:#333;
font-size/* */:/**/small;
font-size: /**/small;
}

5.save template

6.see ur blog

Try Please ^^