.ready()
#posts {margin:0 auto;}
$(window).load(function() { $('#posts').masonry({ itemSelector: '.post', isAnimated: true, isFitWidth: true });});
http://jsfiddle.net/4VfAg/1/
.ready(): http://jsfiddle.net/tovic/4VfAg/3/embedded/result/My advice: Responsive
Demo: http://fiddle.jshell.net/tovic/4VfAg/11/show/light/
Edit: http://jsfiddle.net/tovic/4VfAg/11/