How to remove background image from slider

Hi, i use Dental theme for my website (http://ds-on.org/) and i want to remove the grey background image from the slider. It's not relative to website content. How can i do this? Please help me!!!

Hi!
Proabably, you have to change the background for body in the file style.css:

body {	
	color:#636363;
	font-family:'tahoma';
	position:relative;
	background:url(images/back-slider.png) no-repeat 50% 92px;
}

Now the image is set as a background for it.