Display images horizontal

Im new to css looked a few things up but couldt find a sollution for this one.
i’d like to have the images next to each other, with the small adjustment inline-tabe i got only 2 next to each other but i like to have more.. how?

can anyone help me?

#recent_photos_envelope{margin:0 0 30px 0;}
.recent_photo_image a {float:left;display:inline-table;margin:20px 16px 15px:width:250px;border:1px dashed #888;padding:5px}
.recent_photo_image a:hover {border:1px dashed #000}