--- a/integration/js/common.js	Tue Jun 25 10:46:42 2013 +0200
+++ b/integration/js/common.js	Wed Jun 26 18:21:15 2013 +0200
@@ -4,6 +4,13 @@
        return this.attr(name) !== undefined;
     };
 
+    $('.modal').on('show', function () {
+        var halfWidth = $(this).width() / 2;
+        $(this).css({
+            'margin-left' : - halfWidth +'px'
+        });
+    });
+
 //open modal
     $(document).on('click', 'a.open-modal', function(e){
         e.preventDefault();