Hi Welcome to Sitepoint 
If you want the hover image to show at the right you will need ot remove the overflow:hidden from the main parent. I assume the overflow:hidden was for float clearing so use another method such as this:
Code:
#jsn-content {
overflow:visible;
zoom:1.0;
}
#jsn-content:after {
content:".";
display:block;
height:0;
clear:both;
visibility:hidden;
}
The space around the images is controlled by the margin on this element.
Code:
.hoverBox a { margin:0; }
Stu Nichols had a lot of good css image galleries if you want something that looks a bit nicer.
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