Remove CSS rules from one HTML image

I am working in WordPress and I have an image inside of a post that I would like to remove the CSS formatting from.

There is a rule in my CSS that gives images backgrounds and I am not sure of the HTML required to remove the CSS rules from just this one image.

Any help would be appreciated.

Edit: Right. code would prolly help: Here is the CSS rule that is being given to all the images placed on the site.

/* 3.2 Images */

.entry img, img.thumbnail { 
padding: 4px; 
background: #f6f6f6; 
border:2px solid #fff; 
display: block; 
-moz-box-shadow: 0 1px 2px rgba(0, 0, 0, 0.3);
-webkit-box-shadow: 0 1px 2px rgba(0, 0, 0, 0.3);
box-shadow: 0 1px 2px rgba(0, 0, 0, 0.3); 
transition: all 0.25s ease-in-out; 
-webkit-transition: all 0.25s ease-in-out; 
-moz-transition: all 0.25s ease-in-out; 
}

.entry img:hover, img.thumbnail:hover { 
box-shadow: 0 0 5px rgba( 10, 10, 10, 0.5 ); 
-webkit-box-shadow: 0 0 5px rgba( 10, 10, 10, 0.5 ); 
-moz-box-shadow: 0 0 5px rgba( 10, 10, 10, 0.5 );  
}