what @henkholland refers to, is the line in the html code in the browser:
<div class="photo">
<p><img cl***="aligncenter size-large wp-image-16"
where your setup distorted the word 'class' into 'cl***'.
therefore the style 'aligncenter' is not recognized by the browser, and your image is off-center.
do you run any 'censoring' plugin, or anything that would consider the letters 'ass' as bad?
you could overcome this by putting following into style.css:
.photo img { display:block; margin: 0 auto;
}
it would mean than all images later in your posts would be centered, and you loose the ability to influence the image orientation.