increasing whitespace - css background

i am very new to CSS开发者_Python百科. i need to increase the width of the white space of this:

http://yoursdproperty.com/index.php?option=com_jumi&fileid=8&Itemid=34

the css file is here:

http://yoursdproperty.com/templates/pjo_joomlaforall/css/template_css.css

how do know which element to change?

The page you link to is using the following as a background image:

http://yoursdproperty.com/templates/pjo_joomlaforall/images/bgr.png

To increase the width of the white space, you'll need to modify that image. #background_right is the element that contains the background image.

Also, per Umar's answer, install Firebug.

use firebug. it is a firefox add-on. just download and enable it and click an element to inspect it. you will instantly know everything related to it.

Edit

On you page, you just need to replace the image ../images/bgr.png with a wider white space in it.