Centering Banner Slider In Magento

I'm trying to center the banner slider of this website http://www.myusedwheel.com, but it's not centering correctly. When I open the website it a wide screen, the image stays in the same positions and it doesn't center properly.

My current css code is:

<style type="text/css">
#slider{
    margin-left: 195px !important;
    overflow: hidden;
    position: absolute;
    top: 192px;
    width:960px!important;
    height:173px !important;
}
 
#navigation{
position:relative;
z-index:999;
}
.header-container{
height:385px;
}
#controls{
display:none;
}
</style>

Code (markup):

 

In what browser you see that error? i tried viewing it in firefox and Chrome but i don't see that problem. for some reason i can't enter the site on explorer i am getting error so you should check that.

 

Well.. I guess you changed the css code and made margin auto on left and right.
I was gonna suggess that, it seems good to me.

 

Not seeing the issue you describe in latest version of Firefox. Have you checked your site in all the top browsers; Chrome, Firefox, Opera, IE, Safari, Rockmelt, etc and the earlier versions of each browser?

 

I had fixed the issue before oalddesign replied.