changing the back ground

So what are you thinking of when you say “background”? There are hundreds of elements on your home page.

You could use a plugin that controls the background: https://wordpress.org/plugins/search.php?q=background+manager

Or if you want to change the background in CSS, try this:
Install this Custom CSS Manager plugin http://wordpress.org/plugins/custom-css-manager-plugin and use its “CSS Code” section of the dashboard to hold your CSS modifications:

html body {
    background: none;
}